<PAGE>


                                                                   Exhibit 10.21

                             STOCKHOLDERS' AGREEMENT

      This STOCKHOLDERS' AGREEMENT dated as of February 28, 2000 (the
"Agreement") is among (a) PaperExchange.com, Inc., a Delaware corporation (the
"Corporation"), (b) Hilton Plein, Terrapin Holdings LLC, Kraft Group LLC, PE.com
Holdings LLC, Steven Kaplan, Roger Stone, Roger Stone, as Voting Trustee for
each of Matthew and Karen Kaplan, Lauren G. Stone and Jennifer Stone, Matthew
Kaplan, as Voting Trustee for each of Matthew and Karen Kaplan, Lauren G. Stone
and Jennifer Stone, Kent A. Dolby, Madison Dearborn Capital Partners III, L.P.,
Madison Dearborn Special Equity III, L.P., Special Advisors Fund I, LLC, DBV
Investments, L.P., DSCKW Irrevocable Trust and International Paper Company, and
(c) each other Person who becomes a party to this Agreement (collectively, with
the parties listed in clause (b), the "Stockholders") by executing an Instrument
of Accession in the form attached hereto as Schedule 1 (an "Instrument of
Accession").

      WHEREAS, the holders of all of the shares of the Corporation's capital
stock, which shareholdings as of the date of this Agreement and other options
and warrants of the Stockholders are set forth on Schedule 2 attached hereto,
wish to set forth their relative rights with regard to the transfer of the
Corporation's securities and certain other matters concerning the Corporation's
capital stock and to set forth their agreement as to the voting of such
securities;

      NOW, THEREFORE, the parties to this Agreement hereby agree as follows:

      ss.1. DEFINITIONS. For all purposes of this Agreement, the following terms
shall have the meanings set forth below:

      Affiliate. Affiliate shall mean any Person, directly or indirectly,
through one or more intermediaries, controlling, controlled by, or under common
control with another specified Person. The term "control," as used in the
immediately preceding sentence, shall mean with respect to a corporation or
limited liability company the right to exercise, directly or indirectly, more
than fifty percent (50%) of the voting rights attributable to the controlled
corporation or limited liability company, and, with respect to any individual,
partnership, trust, other entity or association, the possession, directly or
indirectly, of the power to direct or cause the direction of the management or
policies of the controlled entity.

      Accepting Offerees. See Section 2.6E.

      Board of Directors. Board of Directors shall mean the Board of Directors
of the Corporation.

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      Common Stock. Common Stock shall mean the Corporation's common stock, par
value $.001 per share.

      Corporation. See preamble.

      Drag-Along Notice. See Section 2.7.

      Drag-Along Rights. See Section 2.7.

      Family. See Section 2.2.

      Kraft. Kraft shall mean Kraft Group LLC, a Delaware limited liability
company.

      ICG. ICG shall mean Internet Capital Group, Inc., a Delaware corporation.

      Initial Public Offering. See Section 3.6.

      Instrument of Accession. See preamble.

      Offer Notice. See Section 2.6B.

      Offer Period. See Section 2.6D.

      Offer Price. See Section 2.6A.

      Offered Securities. See Section 2.6.

      Offerees. See Section 2.6B.

      PEH. PEH shall mean PE.com Holdings, LLC, a Delaware limited liability
company.

      Permitted Transfer. See Section 2.2.

      Person. Person shall mean an individual, partnership, corporation, limited
liability company, association, trust, joint venture, unincorporated
organization, or any government, governmental department or agency or political
subdivision thereof.

      Proxy. See Section 3.1.

      Purchase Offer. See Section 2.6A.

      Purchaser. See Section 2.6A.

      Right of First Refusal Offer. See Section 2.6B.

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                                      -3-


      Securities. Securities shall mean all outstanding shares of the
Corporation's capital stock, including the Common Stock, whether owned on the
date hereof or hereafter acquired, including upon exercise of any options,
warrants or rights or upon conversion of Securities or otherwise.

      Seller. See Section 2.6.

      Stockholders. See preamble.

      Tag-Along Offer. See Section 2.6E.

      Transfers. See Section 2.1.

      ss.2. TRANSFER AND ASSIGNMENT OF SECURITIES.

      2.1 General. A Stockholder shall be entitled to transfer, assign, convey,
sell, encumber or in any way alienate all or any portion of its Securities
(collectively, "Transfer") only as provided in this Section 2. After the
consummation of any Transfer of all or any portion of its Securities, the
Securities so transferred shall continue to be subject to the terms and
provisions of this Agreement and any further Transfers shall be required to
comply with all the terms and provisions of this Agreement.

      2.2 Permitted Transfers. A Stockholder shall be entitled to engage in the
following Transfers, each of which may be undertaken and consummated without
compliance with the restrictions set forth in Section 2.6: (i) Transfers to a
Stockholder's Family (as defined in this Section 2.2 below), including without
limitation, Transfers to Family for estate planning purposes; (ii) Transfers by
Kraft or any Affiliate of Kraft; (iii) Transfers by ICG to the extent required
to perfect security interests of its institutional lenders under credit
agreements, if ICG becomes a Stockholder; (iv) Transfers by PEH to ICG; and (v)
Transfers to Affiliates (each a "Permitted Transfer" and collectively the
"Permitted Transfers"). With respect to any Permitted Transfer by Kraft or any
Affiliate of Kraft, solely pursuant to clause (ii) of this Section 2.2, Kraft or
any Affiliate of Kraft shall be subject to the provisions of Section 2.6C if the
Securities to be transferred, individually or collectively in a single Transfer
or series of related Transfers, constitute 5% or more of the Securities on a
fully diluted basis. "Family" shall include only such transferor's spouse,
ancestors and lineal discendants (including adoptive individuals as lineal
descendents) and trusts for any such Person's or Persons' exclusive benefit.

      2.3 Restrictions on Transfer of Securities. In addition to other
restrictions set forth in this Agreement, no Stockholder shall Transfer all or
any portion of its Securities without compliance with all federal and state
securities law.

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                                      -4-


      2.4 Conditions to Transfer. No Transfer shall be permitted hereunder
unless (i) the transferee, including, but not limited to, ICG upon the
completion of a Transfer from PEH pursuant to Section 2.2(iv), shall become a
party to this Agreement by executing and delivering to the Corporation an
Instrument of Accession, which executed Instrument of Accession shall thereupon
become a part of this Agreement, (ii) the requirements of Section 2.3 relating
to securities requirements hereof are met, and (iii) the transferee pays any
reasonable expenses in connection with its becoming a new Stockholder. A
Transfer to a new Stockholder shall not result in the release of the Stockholder
who assigned the Securities from any liability that such Stockholder may have to
the Corporation.

      2.5 Rights of Legal Representatives. If a Stockholder who is an individual
dies or is adjudged by a court of competent jurisdiction to be incompetent to
manage the Stockholder's person or property, the Stockholder's executor,
administrator, guardian, conservator, or other legal representative may exercise
all of the Stockholder's rights for the purpose of settling the Stockholder's
estate or administering the Stockholder's property. If a Stockholder is a
corporation, trust, or other entity and is dissolved or terminated, the powers
of that Stockholder may be exercised by its legal representative or successor.

      2.6 Additional Rights of Purchase and Sale. In addition to the other
limitations and restrictions set forth in this Section 2, no Stockholder shall
Transfer all or any portion of his Securities (the "Offered Securities") unless
such Stockholder (the "Seller") first complies with the provisions of this
Section 2.6. This Section 2.6 shall not apply to a Permitted Transfer.

            A. Limitation on Transfers. No Transfer may be made under this
Section 2.6 unless the Seller has received a bona fide written offer (the
"Purchase Offer") from a Person (the "Purchaser") to purchase the Offered
Securities for a purchase price (the "Offer Price") denominated and payable in
United States dollars at closing or according to specified terms, with or
without interest, which offer shall be in writing signed by the Purchaser and
shall be irrevocable for a period ending no sooner than the day following the
end of the Offer Period (as hereinafter defined).

            B. Offer Notice. Prior to making any Transfer that is subject to the
terms of this Section 2.6, the Seller shall give to the Corporation and each
other Stockholder written notice (the "Offer Notice") which shall include a copy
of the Purchase Offer and an offer (the "Right of First Refusal Offer") to sell
the Offered Securities to the other Stockholders (the "Offerees") for the Offer
Price, payable according to the same terms as (or more favorable terms than)
those contained in the Purchase Offer, provided that the Right of First Refusal
Offer shall be made without regard to the requirement of any earnest money or
similar deposit required of the Purchaser prior to closing, and without regard
to any security (other than the

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                                      -5-


Offered Securities) to be provided by the Purchaser for any deferred portion of
the Offer Price.

            C. Tag-Along Offer. If the Offered Securities (which in the case of
Kraft or an Affiliate of Kraft, includes a Permitted Transfer under Section
2.2(ii)) constitute 5% or more of the Securities on a fully diluted basis, the
Offer Notice shall include an offer (the "Tag-Along Offer") to the Offerees to
participate in the proposed sale to the Purchaser as to a portion of the
Offerees' Securities. Each Offeree shall have the right to sell a portion of his
Securities pursuant to the terms of the Purchase Offer, such portion to be
determined by multiplying the number of Offered Securities by a fraction, the
numerator of which is the number of Securities then owned by the Offeree, and
the denominator of which is the number of Securities owned by all Stockholders.
To the extent an Offeree exercises his right to participate in the proposed sale
to the Purchaser, the Securities that may be sold by the Seller shall be reduced
proportionately.

            D. Offer Period. The Right of First Refusal Offer and the Tag-Along
Offer shall be irrevocable for a period (the "Offer Period") ending at 11:59
P.M., local time at the Corporation's principal office, on the 20th day
following the day of the Offer Notice.

            E. Acceptance of Offer. At any time during the first 15 days of the
Offer Period, any Offeree may accept: (i) the Right of First Refusal Offer as to
all or any percentage of that portion of the Offered Securities that corresponds
to the ratio of his Securities to the total Securities held by all Offerees, or
(ii) the Tag-Along Offer in an amount not to exceed the maximum number of
Securities with respect to which the Offeree may participate as set forth in
Section 2.6C, in each case by giving written notice of such acceptance to the
Seller and the Board of Directors.

            At any time after the 15th day of the Offer Period, but within the
20 day period set forth in Section 2.6D, Offerees who had previously accepted
the Right of First Refusal Offer pursuant to the previous sentence ("Accepting
Offerees") may accept the Right of First Refusal Offer as to any portion of the
Offered Securities that has not been previously accepted by giving written
notice of such acceptance to the Seller and the Board of Directors. In the event
Accepting Offerees so accept the Right of First Refusal Offer with respect to
more than the balance of the Offered Securities, then the balance of the Offered
Securities shall be allocated among such Accepting Offerees in proportion to
their number of Securities. In the event that Offerees, in the aggregate, accept
the Right of First Refusal Offer with respect to all of the Offered Securities,
the Right of First Refusal Offer shall be deemed to be accepted. If Offerees do
not accept the Right of First Refusal Offer as to all of the Offered Securities
during the Offer Period, the Right of First Refusal Offer shall be deemed to be
rejected in its entirety.

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                                      -6-


            If the Right of First Refusal Offer is deemed to be rejected in its
entirety pursuant to the preceding paragraph, the Offerees nevertheless may
participate in the sale to the Purchaser pursuant to their exercise of the
Tag-Along Offer as set forth above, and the Offerees who accepted the Tag-Along
Offer shall be treated as Accepting Offerees for purposes of this Section 2.6.
If the Right of First Refusal Offer is accepted with respect to all of the
Offered Securities, those Stockholders exercising the Right of First Refusal
Offer shall purchase the Offered Securities as provided in this Section 2.6, and
the Tag-Along Offer shall become null and void.

            F. Closing of Purchase Pursuant to Right of First Refusal Offer or
Tag-Along Offer. In the event that the Right of First Refusal Offer is accepted,
the closing of the sale of the Offered Securities shall take place within 30
days after the Right of First Refusal Offer is accepted or, if later, the date
of closing set forth in the Purchase Offer. The Seller and all Accepting
Offerees shall execute such documents and instruments as may be necessary or
appropriate to effect the sale of the Offered Securities pursuant to the terms
of the Right of First Refusal Offer or the Tag-Along Offer and this Section 2.6.

            G. Sale Pursuant to Purchase Offer If Right of First Refusal Offer
is Rejected. If the Right of First Refusal Offer is not accepted in the manner
set forth in this Section 2.6, the Seller and any Accepting Offerees who
accepted the Tag-Along Offer may sell to the Purchaser an aggregate number of
Securities not to exceed the Securities representing the Offered Securities at
any time within 60 days after the last day of the Offer Period, provided that
such sale shall be made on terms no more favorable to the Purchaser than the
terms contained in the Purchase Offer and provided further that such sale
complies with other terms, conditions and restrictions of this Agreement that
are applicable to Transfers of Securities. In the event that the Offered
Securities are not sold in accordance with the terms of the preceding sentence,
the Offered Securities shall again become subject to all of the conditions and
restrictions of this Section 2.6.

      2.7 Drag-Along Rights. If Kraft proposes to enter into a transaction or
series of related transactions as a result of which all Securities of Kraft and
its Affiliates will be transferred to one or more third parties (other than
persons who are then Stockholders or Affiliates of Stockholders), Kraft shall
have the right to drag-along with Kraft and its Affiliates all of the Securities
then outstanding on the same terms, for the same form of consideration and for
the same price per share as Kraft and its Affiliates are to receive for the
Securities owned by them. This right to cause the sale of Securities of other
Stockholders as set forth in this Section 2.7 shall be referred to as
"Drag-Along Rights". Kraft shall exercise its Drag-Along Rights under this
Section 2.7 by delivering a notice (the "Drag-Along Notice") to all Stockholders
no later than 30 days prior to the date the proposed transaction is

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                                      -7-


contemplated to close. The Drag-Along Notice shall include the following
statements or information: (i) Kraft's bonafide intention to sell or transfer
its Securities; (ii) the number of Securities to be sold or transferred; (iii)
the price and salient terms of such sale or transfer; (iv) the name of the
proposed transferee; and (v) a copy of all transaction documents in
substantially final form; provided, however, that such transaction documents
need only be delivered within five business days of the date the proposed
transaction is contemplated to close. For purposes of this Section, if such
Drag-Along Notice is served personally or by facsimile transmission, delivery
shall be conclusively deemed made at the time of such personal service or at the
time the notice is transmitted. If such Drag-Along Notice is given via
registered mail, return receipt request, delivery shall be conclusively deemed
given five (5) business days after the deposit thereof in the United States
mail. If such Drag-Along Notice is given by overnight mail, delivery shall be
conclusively deemed made on the next business day after mailing. If a Drag-Along
Notice is given, but the transaction is not consummated within 90 days of the
date of such notice, such notice will no longer be valid and a new Drag-Along
Notice shall be required. If a transaction which is subject to Krafts'
Drag-Along Rights is pending, a majority of the members of the Board of
Directors may designate one or more representatives to act as attorney-in-fact
for each Stockholder who is subject to the Drag-Along Rights, as set forth in
Section 5, and each such representative shall have the power-of-attorney (such
power to be irrevocable and coupled with an interest) to execute such documents
and take such actions as such representative may deem necessary or advisable in
order to affect the Drag-Along Rights granted under this Section 2.7.

      2.8 Transfers of Securities in Breach of this Agreement. In the event of
any Transfer of Securities in breach of this Agreement, commencing immediately
upon the date of such attempted Transfer (i) such Transfer shall be void and of
no effect; (ii) no dividend of any kind or any distribution pursuant to any
liquidation, redemption or otherwise shall be paid by the Corporation to the
purported transferee in respect of such Securities (all such rights to payment
by the transferring Stockholder and/or the purported transferee being deemed
waived); (iii) the voting rights of such Securities, if any, shall terminate;
and (iv) neither the transferring Stockholder nor the purported transferee shall
be entitled to exercise any rights with respect to such Securities until such
Transfer in breach of this Agreement has been rescinded.

      ss.3. PROXY AND VOTING AGREEMENT.

      3.1 Proxy; Voting Agreement. (a) Each Stockholder, except Kraft, hereby
grants to the Board of Directors (the "Proxy") an irrevocable proxy coupled with
an interest, with full power of substitution, to vote all Securities held by
such Stockholder with respect to any matter on which the Stockholder has the
right to

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                                      -8-


vote or give its consent, approval or authorization or to call a meeting under
the Delaware General Corporation Law, the Certificate of Incorporation or
By-laws of the Corporation or this Agreement, except under Section 14 of this
Agreement, with all powers that the Stockholder would possess if personally so
voting, consenting, approving or authorizing and as the Proxy so chooses. This
proxy will survive a Stockholder's death, incapacity or dissolution. This proxy
shall expire on the earlier of (i) February 1, 2015 and (ii) the termination of
this Agreement pursuant to Section 15. Each Stockholder acknowledges and agrees
that this proxy is coupled with an interest sufficient in law to support an
irrevocable power. Only a majority vote of the Board of Directors shall be
necessary to take action as the Proxy.

      (b) Further, the Stockholders, except for Kraft, agree that they will not
take any action as stockholders of the Corporation, except for Transfers
pursuant to the terms of this Agreement, unless such action is first approved by
the Board of Directors.

      3.2 All Securities. For the avoidance of doubt, the provisions of this
Agreement shall apply to any and all Securities owned by the Stockholders on the
date hereof and hereafter acquired.

      3.3 New Stockholders. Also for the avoidance of doubt, in the event that a
Person becomes a party to this Agreement after the date hereof, by executing and
delivering an Instrument of Accession, such Person shall be deemed to have
appointed the Proxy as its proxy for purposes of Section 3.1.

      3.4 Board of Directors. (a) Notwithstanding anything herein or in the
Certificate of Incorporation or By-Laws of the Corporation to the contrary but
subject to amendment pursuant to Section 14, the Corporation and the
Stockholders agree that with respect to any and all elections of directors of
the Corporation (whether at a meeting or by written consent in lieu of a
meeting), all Securities owned by the Stockholders shall be voted by the Proxy
so as to fix the number of directors of the Corporation at eight (8), and to
nominate and elect such eight (8) directors of the Corporation as follows:

            (i) Six (6) individuals designated by Kraft so long as Kraft is a
      stockholder of the Corporation; and

            (ii) Two (2) individuals designated by PEH so long as PEH is a
      stockholder of the Corporation or by ICG if ICG becomes a Stockholder
      pursuant to Section 2.2(iv) so long as ICG is a stockholder of the
      Corporation.

            (b) If any vacancy shall occur in the Board of Directors of the
Corporation as a result of death, disability, resignation or any other
termination of a director, the replacement for such vacating director shall be
designated by the

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                                      -9-


Person or Persons who, pursuant to Section 3.4(a) above, originally designated
such vacating director. Each Person or Persons entitled to designate a director
or a replacement for a director pursuant to this Section 3.4 shall also be
entitled to designate the removal of such director with or without cause at any
time, and from time to time, in its sole discretion. Each Stockholder agrees
that the Proxy shall vote all Securities owned by such Stockholder in order to
comply with this Section 3.4.

      3.5 Proxy's Indemnity.

            (a) The Proxy shall serve without compensation and shall have the
right to incur and pay and the Corporation, at the Proxy's request, agrees to
advance such reasonable expenses and charges, and to employ and pay and the
Corporation, at the Proxy's request, agrees to advance payment of such agents,
attorneys, and counsel as it may deem necessary and proper for carrying out this
Agreement. Any such expenses and charges incurred by and due to the Proxy shall
be paid by the Corporation.

            (b) The Proxy assumes no liability as a Stockholder, its interest
hereunder being that of a proxy only. In voting the Securities (which it may do
either in person or by proxy as aforesaid), the Proxy will vote and act in all
matters in accordance with its good faith judgment and the terms of this
Agreement; but it assumes no responsibility or liability in respect of any
action taken by it or in pursuance of its vote so cast, and the Proxy shall not
incur any responsibility or liability by reason of any error of fact or law,
mistake of judgment, or of any matter or thing done or suffered or omitted to be
done under this Agreement, except for its own individual willful misconduct.

            (c) The Proxy shall not be answerable for the default or misconduct
of any agent or attorney appointed by it in pursuance hereof if such agent or
attorney shall have been selected with reasonable care.

            (d) The Corporation hereby agrees that it will at all times protect,
indemnify and save harmless the Proxy from any loss, cost or expense of any kind
or character whatsoever incurred in connection with the proxies granted pursuant
to Section 3.1 except those, if any, arising from the willful misconduct of the
Proxy, and will at all times itself undertake, assume full responsibility for,
pay and advance all costs and expenses of any suit or litigation of any
character, including any proceedings before any governmental agency, with
respect to the Securities or this Agreement and, if the Proxy shall be made a
party thereto, the Corporation will pay and advance all costs and expenses,
including counsel fees, to which the Proxy may be subject by reason thereof.

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            (e) Notwithstanding any other provision hereof, the provisions of
this Section 3.5 shall survive the termination of this Agreement.

      3.6 Classes of Directors. The Corporation and the Stockholders acknowledge
and agree that in connection with a proposed underwritten public offering
pursuant to an effective registration statement under the Securities Act of
1933, as amended, covering the offer and sale of shares of Common Stock
("Initial Public Offering"), the Certificate of Incorporation and/or By-laws of
the Corporation may be amended to permit classes of directors with staggered
terms and the Proxy grants the Board of Directors the right to vote all
Securities held by the Stockholders (other than Kraft) in favor of such an
amendment.

      ss.4. PREEMPTIVE RIGHTS. With the exception of (a) shares of Common Stock
issued to employees of the Corporation pursuant to an employee option plan or
other employee benefit plan approved by the Board of Directors, (b) shares of
Common Stock issued upon exercise of the warrants and options set forth on
Schedule 2 attached hereto, and (c) up to 450,000 shares of Common Stock issued
upon exercise of additional options issued to Kraft and/or other any persons or
entities designated by Kraft, in conjunction with any proposed issuance of
additional Securities to any party, each Stockholder shall have the pro rata
right to acquire a pro rata number of additional Securities so that such
Stockholder's proportional interest in the Corporation (without giving effect to
any outstanding options or warrants or other rights to purchase) will not be
diluted; provided that this preemptive right shall not apply to the extent that
a Stockholder holds shares of Common Stock issued to employees of the
Corporation pursuant to (or resulting from the exercise of any option granted
under) an employee option plan or other employee benefit plan approved by the
Board of Directors, including any such plan that replaced any similar plan of
PaperExchange.com, LLC, the Delaware limited liability company from which the
Corporation was converted. (For the avoidance of doubt, the option for 1,767,020
shares of Common Stock issued to Kent A. Dolby on December 20, 1999 was not
issued pursuant to an employee option plan or other employee benefit plan
approved by the Board of Directors.) Any exercise of preemptive rights pursuant
to this Section 4 must be made within 10 days of receiving written notice of the
proposed issuance of additional Securities. The Stockholders understand and
agree that if a Stockholder does not exercise the preemptive rights set forth in
this Section 4 in conjunction with any issuance of additional Securities, such
Stockholder's ownership interest and voting rights will be diluted.

      ss.5. SPECIAL POWER OF ATTORNEY.

      A. Attorney in Fact. Each Stockholder hereby grants to the Board of
Directors of the Corporation a special power of attorney irrevocably making,
constituting and appointing the Board of Directors as the Stockholder's attorney
in

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                                      -11-


fact, with all power and authority to act in the Stockholder's name and on the
Stockholder's behalf and to execute, acknowledge and deliver and swear to in the
execution, acknowledgement, delivery and filing of assignments of Securities or
any other instrument or document that may be reasonably required by the Board of
Directors to effect a transfer whenever a Stockholder is legally obligated to
transfer such Stockholder's Securities under Section 2 of this Agreement but is
unable or unwilling to execute, acknowledge, deliver or swear to an assignment
of Securities necessary to effect such a transfer.

      B Irrevocable Power. The special power granted in Section 5A: (I) is
irrevocable; and (ii) shall survive a Stockholder's death, incapacity or
dissolution.

      C. Signatures. The Board of Directors may exercise the special power of
attorney granted in Section 5A by an original or facsimile signature of one or
more members of the Board of Directors of the Corporation.

      ss.6. ADDITIONAL LEGENDS. So long as any Securities are subject to the
provisions hereof, all certificates or instruments representing Securities will
have imprinted on them the following legend:

                  "THE SHARES EVIDENCED BY THIS CERTIFICATE HAVE NOT BEEN
            REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED. NO
            TRANSFER, SALE OR OTHER DISPOSITION OF THESE SHARES MAY BE MADE
            UNLESS A REGISTRATION STATEMENT WITH RESPECT TO THESE SHARES HAS
            BECOME EFFECTIVE UNDER SAID ACT, OR THE CORPORATION HAS BEEN
            FURNISHED WITH AN OPINION OF COUNSEL SATISFACTORY TO THE CORPORATION
            THAT SUCH REGISTRATION IS NOT REQUIRED.

                  THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO THE
            TERMS OF A CERTAIN STOCKHOLDERS' AGREEMENT, DATED AS OF FEBRUARY 28,
            2000, AMONG THE CORPORATION AND ITS STOCKHOLDERS. THE STOCKHOLDERS'
            AGREEMENT CONTAINS CERTAIN RESTRICTIVE PROVISIONS RELATING TO THE
            VOTING AND TRANSFER OF SHARES OF THE STOCK REPRESENTED HEREBY,
            INCLUDING AN IRREVOCABLE PROXY. A COPY OF THE STOCKHOLDERS'
            AGREEMENT IS ON FILE AT THE CORPORATION'S PRINCIPAL OFFICES. UPON
            WRITTEN REQUEST TO THE CORPORATION'S SECRETARY, A COPY OF THE
            STOCKHOLDERS' AGREEMENT WILL BE PROVIDED

<PAGE>
                                      -12-


            WITHOUT CHARGE TO APPROPRIATELY INTERESTED PERSONS."

      ss.7. SEVERABILITY. Whenever possible, each provision of this Agreement
will be interpreted in such manner as to be effective and valid under applicable
law, but if any provision of this Agreement is held to be invalid, illegal or
unenforceable in any respect under any applicable law or rule in any
jurisdiction, such invalidity, illegality or unenforceability will not affect
any other provision or any other jurisdiction, but this Agreement will be
reformed, construed and enforced in such jurisdiction as if such invalid,
illegal or unenforceable provision had never been contained herein.

      ss.8. ENTIRE AGREEMENT. Except as otherwise expressly set forth herein,
this document embodies the complete agreement and understanding among the
parties hereto with respect to the subject matter hereof and thereof and
supersedes and preempts any prior understandings, agreements or representations
by or among the parties, written or oral, which may have related to the subject
matter hereof in any way.

      ss.9. SUCCESSORS AND ASSIGNS. This Agreement will bind and inure to the
benefit of and be enforceable by the Corporation and the Stockholders and their
respective successors and assigns.

      ss.10. NEW STOCKHOLDERS. Except for issuance of Securities to any Person
who is a Stockholder prior to giving effect to such issuance, the Corporation
will not issue any shares of capital stock or any rights to purchase the same or
enter into any commitment, conditional or otherwise, to do so unless the holder
or transferee of such stock or commitment shall have first executed an
Instrument of Accession.

      ss.11. COUNTERPARTS. This Agreement may be executed in separate
counterparts each of which will be an original and all of which taken together
will constitute one and the same agreement.

      ss.12. REMEDIES. The Stockholders will be entitled to enforce their rights
under this Agreement specifically (without posting a bond or other security), to
recover damages by reason of any breach of any provision of this Agreement and
to exercise all other rights existing in their favor. The parties hereto agree
and acknowledge that money damages may not be an adequate remedy for any breach
of the provisions of this Agreement and that any Stockholder may in its sole
discretion apply to any court of law or equity of competent jurisdiction for
specific performance and/or injunctive relief in order to enforce or prevent any
violation of the provisions of this Agreement. In the event of any dispute
involving the terms of this Agreement, the prevailing party shall be entitled to
collect reasonable fees and

<PAGE>
                                      -13-


expenses incurred by the prevailing party in connection with such dispute from
the other parties to such dispute.

      ss.13. NOTICES. Any notice provided for in this Agreement will be in
writing and will be deemed properly delivered if either personally delivered or
sent by telecopier, overnight courier or mailed certified or registered mail,
return receipt requested, postage prepaid to the recipient (a) if to any
Stockholder, at the address listed for such Stockholder in the stock records of
the Corporation, and (b) if to the Corporation, to PaperExchange.com, Inc., 545
Boylston Street, 8th Floor, Boston, Massachusetts 02116, Attention: President.
Any such notice shall be effective (i) if delivered personally or by telecopier,
when received, (ii) if sent by overnight courier, when receipted for, and (iii)
if mailed, five days after being mailed as described above. The Corporation
agrees to make available to each Stockholder upon request an address list of all
Stockholders to ensure correct delivery of all notices hereunder.

      ss.14. AMENDMENT AND WAIVER. No modification, amendment or waiver of any
provision of this Agreement will be effective against either of the Corporation
or the Stockholders unless such modification, amendment or waiver is approved in
writing by Stockholders owning 51% or more of the Securities; provided that the
approval of Kraft and PEH (so long as PEH is a stockholder of the Corporation or
ICG, if ICG becomes a Stockholder pursuant to Section 2.2(iv), so long as ICG is
a stockholder of the Corporation) or, if PEH, subject to the immediately
preceding parenthetical, does not so approve, the approval of Stockholders
owning 80% or more of the Securities, shall be required in connection with any
modification, amendment or waiver to Sections 2.2, 2.6, 3.4, 4 or 14 or any
modification, amendment or waiver to Section 2.7 that would make the drag-along
rights described therein applicable to transfers to persons who are then
Stockholders or Affiliates of Stockholders; provided further that any
modification, amendment or waiver shall require the approval of Kraft so long as
Kraft is a stockholder of the Corporation. The failure of any party to enforce
any of the provisions of this Agreement will in no way be construed as a waiver
of such provisions and will not affect the right of such party thereafter to
enforce each and every provision of this Agreement in accordance with its terms.

      ss.15. TERMINATION. This Agreement will terminate upon the completion of
any voluntary or involuntary liquidation or dissolution of the Corporation or
upon an Initial Public Offering.

      ss.16. LOCKUP AGREEMENT. Each Stockholder, if requested by the Corporation
or an underwriter of any Securities, shall agree not to sell or otherwise
transfer or dispose of any Securities held by such Stockholder for a specified
period of time (not to exceed 180 days unless otherwise agreed to) following the
effective date of a registration statement. Such agreement shall be in writing
in a form

<PAGE>
                                      -14-


reasonably satisfactory to the Corporation and such underwriter. Such agreement
shall be applicable only to the registration statement of the Corporation that
covers Securities to be sold on its behalf to the public in the initial
underwritten public offering.

      ss.17. GOVERNING LAW. THE LAWS OF THE STATE OF DELAWARE SHALL GOVERN THE
VALIDITY OF THIS AGREEMENT, THE CONSTRUCTION OF ITS TERMS, AND THE
INTERPRETATION OF THE RIGHTS AND DUTIES OF THE BOARD OF DIRECTORS AND THE
STOCKHOLDERS.

      ss.18. DESCRIPTIVE HEADINGS. The descriptive headings of this Agreement
are inserted for convenience only and do not constitute a part of this
Agreement.

<PAGE>
                                      -15-


      IN WITNESS WHEREOF, the parties hereto have executed this Stockholders'
Agreement on the day and year first above written.

                                    PAPEREXCHANGE.COM, INC.

                                    By: /s/ Kent A. Dolby
                                        ----------------------------------------
                                        Kent A. Dolby
                                        President


                                    STOCKHOLDERS:

                                    /s/ Hilton Plein
                                    ----------------------------------
                                    HILTON PLEIN


                                    TERRAPIN HOLDINGS LLC

                                    By: /s/ Jason Weiss
                                        ----------------------------------------
                                        Name: Jason Weiss
                                        Title: Manager


                                    KRAFT GROUP LLC,

                                    By: Kraft Family Inc., Its Managing Member

                                    By: /s/ Robert K. Kraft
                                        ----------------------------------------
                                        Robert K. Kraft
                                        President

<PAGE>
                                      -16-


                                    PE.COM HOLDINGS LLC

                                    By: /s/ Gregory W. Haskell
                                        ----------------------------------------
                                        Name: Gregory W. Haskell
                                        Title: Director

                                    /s/ Steven Kaplan
                                    ----------------------------------
                                        Steven Kaplan

                                    /s/ Roger Stone
                                    ----------------------------------
                                        Roger Stone

                                    /s/ Roger Stone
                                    ----------------------------------
                                        Roger Stone, as Voting Trustee for each
                                        of Matthew and Karen Kaplan, Lauren G.
                                        Stone and Jennifer Stone

                                    /s/ Matthew Kaplan
                                    ----------------------------------
                                        Matthew Kaplan, as Voting Trustee for
                                        each of Matthew and Karen Kaplan, Lauren
                                        G. Stone and Jennifer Stone

                                    /s/ Kent A. Dolby
                                    ----------------------------------
                                        Kent A. Dolby

<PAGE>
                                      -17-


                                    MADISON DEARBORN CAPITAL
                                    PARTNERS III, L.P.,

                                    By: Madison Dearborn Partners III, L.P.,
                                        its general partner

                                        By: Madison Dearborn Partners, LLC, its
                                            general partner

                                            By: /s/ Samuel M. Mencoff
                                                --------------------------------
                                                Samuel M. Mencoff
                                                Managing Director


                                    MADISON DEARBORN SPECIAL
                                    EQUITY III, L.P.,

                                    By: Madison Dearborn Partners III, L.P.,
                                        its sole general partner

                                        By: Madison Dearborn Partners, LLC, its
                                            sole general partner

                                            By: /s/ Samuel M. Mencoff
                                                --------------------------------
                                                Samuel M. Mencoff
                                                Managing Director


                                    SPECIAL ADVISORS FUND I, LLC,

                                    By: Madison Dearborn Partners, LLC,
                                        its manager

                                        By: /s/ Samuel M. Mencoff
                                            ------------------------------------
                                            Samuel M. Mencoff
                                            Managing Director

<PAGE>
                                      -18-


                                    DBV INVESTMENTS, L.P.,

                                    By: DRT Capital, L.L.C.,
                                        its general partner

                                        By: /s/ John Phelan
                                            ------------------------------------
                                        Name: John Phelan
                                              ----------------------------------
                                        Title: Manager
                                               ---------------------------------


                                    DSCKW IRREVOCABLE TRUST

                                    By: /s/ A. Parafestas
                                        ----------------------------------------
                                        Anastasios Parafestas, Trustee


                                    INTERNATIONAL PAPER COMPANY

                                        By: /s/ C. Cato Early
                                            ------------------------------------
                                        Name: C. Cato Early
                                              ----------------------------------
                                        Title: Vice President
                                               ---------------------------------

<PAGE>

                                                                      Schedule 1

                             Instrument of Accession

      The undersigned, ____________________, in order to become the owner or
holder of ________ shares of Common Stock, $.001 par value per share (the
"Shares"), of PaperExchange.com, Inc., a Delaware corporation, hereby agrees to
become a Stockholder party to that certain Stockholders' Agreement, dated as of
February __, 2000 (the "Stockholders' Agreement"), a copy of which is attached
hereto. The undersigned acknowledges that the Shares constitute shares of
"Securities" and the undersigned shall be a "Stockholder" under and as defined
in the Stockholders' Agreement. This Instrument of Accession shall become a part
of such Stockholders' Agreement.

      Executed as of the date set forth below under the laws of the State of
Delaware.


                                        Signature:
                                                   -----------------------------
                                        Address:
                                                 -------------------------------
                                                 -------------------------------
                                                 -------------------------------

                                        Date:
                                              ----------------------------------

Accepted:

PAPEREXCHANGE.COM, INC.


By:
    ----------------------
Date:
      --------------------