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                                                                    EXHIBIT 4.20
 
                           SIXTH WAIVER AND AMENDMENT
 
     SIXTH WAIVER AND AMENDMENT (this "Amendment"), dated as of July 24, 1998,
among American Pad & Paper Company ("Holdings"), WR Acquisition, Inc. ("WR
Acquisition"), American Pad & Paper Company of Delaware, Inc. (the "Borrower"),
the lending institutions party to the Credit Agreement referred to below (each a
"Bank" and, collectively, the "Banks"), Bank of Tokyo-Mitsubishi Trust Company,
Bank One Texas, N.A., The Bank of Nova Scotia and The First National Bank of
Boston, as Co-Agents (the "Co-Agents"), and Bankers Trust Company, as Agent (the
"Agent"). All capitalized terms used herein and not otherwise defined herein
shall have the respective meanings provided such terms in the Credit Agreement.
 
                                  WITNESSETH:
 
     WHEREAS, Holdings, WR Acquisition, the Borrower, the Banks, the Co-Agents
and the Agent are party to a Credit Agreement, dated as of July 8, 1996 (as
amended, modified and supplemented prior to the date hereof, the "Credit
Agreement");
 
     WHEREAS, Holdings, WR Acquisition, the Borrower, the Banks, the Co-Agents
and the Agent are party to the Fifth Waiver and Amendment, dated as of June 30,
1998 (the "Fifth Amendment"); and
 
     WHEREAS, the Borrower has requested that the Banks provide the amendment
provided for herein and the Banks have agreed to provide such amendment on the
terms and conditions set forth herein;
 
     NOW, THEREFORE, it is agreed:
 
          1. The Waiver Termination Date (as defined in the Fifth Amendment) is
     hereby extended to September 30, 1998.
 
          2. Section 8.06(a) of the Credit Agreement is hereby amended by
     inserting the following proviso at the end thereof:
 
        "; provided that (i) Foreign Subsidiaries may not hold Foreign Cash
        Equivalents in excess of $25,000 (or the equivalent thereof in foreign
        currencies) at any time and (ii) 100% of all cash and Cash Equivalents
        held by the Borrower and its Subsidiaries (other than the Receivables
        Entity) at any time (other than up to $1,000,000 of cash and Cash
        Equivalents, including without limitation cash and Cash Equivalents
        pledged or deposited in accordance with Section 8.03(f)) must be held in
        one or more accounts maintained with the Agent or a Bank."
 
          3. Each Bank hereby agrees that for the purposes of Section 5.02 of
     the Credit Agreement, any amendment or waiver of a Default or an Event of
     Default, the effect of which would be to allow the sum of (i) the aggregate
     outstanding principal amount of Revolving Loans and Swingline Loans and
     (ii) the Letter of Credit Outstandings under the Credit Agreement to exceed
     $300,000,000, shall not be effective without the consent of the
     Supermajority Banks (it being understood and agreed that any Default or
     Event or Default that may be otherwise waived or amended with the consent
     of the Required Banks may still be waived or amended by the Required Banks
     for any purpose other than for the purpose set forth above in this Section
     3).
 
          4. The following definition is hereby inserted into Section 10 of the
     Credit Agreement in alphabetical order:
 
             "Supermajority Banks" shall mean collectively (and not
        individually) Non-Defaulting Banks the sum of whose Revolving Loan
        Commitments (or, if after the Total Revolving Loan Commitment has been
        terminated, outstanding Revolving Loans and Percentages of outstanding
        Swingline Loans and Letter of Credit Outstandings) constitute greater
        than 66 2/3% of the Total Revolving Loan Commitment less the aggregate
        Revolving Loan Commitments of Defaulting Banks (or, if after the Total
        Revolving Loan Commitment has been terminated, the total outstanding
        Revolving Loans of
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        Non-Defaulting Banks and the aggregate Percentages of all Non-Defaulting
        Banks of the total outstanding Swingline Loans and Letter of Credit
        Outstandings at such time).
 
          5. In order to induce the Banks to enter into this Amendment, the
     Borrower hereby agrees to pay to each Bank which executes and delivers a
     counterpart of this Amendment on or before 5:00 p.m. (New York time) on
     July 30, 1998, a fee equal to 1/8 of 1% of such Bank's Revolving Loan
     Commitment, such fee to be earned and payable on the Amendment Effective
     Date.
 
          6. In order to induce the Banks to enter into this Amendment, each of
     Holdings, WR Acquisition and the Borrower hereby represents and warrants
     that (i) no Default or Event of Default exists as of the Amendment
     Effective Date (as defined below) after giving effect to this Amendment and
     (ii) on the Amendment Effective Date, both before and after giving effect
     to this Amendment, all representations and warranties contained in the
     Credit Agreement and in the other Credit Documents are true and correct in
     all material respects.
 
          7. This Amendment shall become effective on the date (the "Amendment
     Effective Date") when the Required Banks, Holdings, WR Acquisition and the
     Borrower shall have signed a counterpart hereof (whether the same or
     different counterparts) and shall have delivered (including by way of
     facsimile transmission) the same to the Agent at its Notice Office.
 
          8. This Amendment is limited as specified and shall not constitute a
     modification, acceptance or waiver of any other provision of the Fifth
     Amendment, the Credit Agreement or any other Credit Document.
 
          9. This Amendment may be executed in any number of counterparts and by
     the different parties hereto on separate counterparts, each of which
     counterparts when executed and delivered shall be an original, but all of
     which shall together constitute one and the same instrument. A complete set
     of counterparts shall be lodged with the Borrower and the Agent.
 
          10. All references in the Credit Agreement and each of the Credit
     Documents to the Credit Agreement shall be deemed to be references to such
     Credit Agreement after giving effect to this Amendment.
 
          11. THIS AMENDMENT AND THE RIGHTS AND OBLIGATIONS OF THE PARTIES
     HEREUNDER SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF
     THE STATE OF NEW YORK.
 
                                    -  -  -
 
     IN WITNESS WHEREOF, each of the parties hereto has caused a counterpart of
this Amendment to be duly executed and delivered as of the date hereof.
 
                                            AMERICAN PAD & PAPER COMPANY
 
                                            By:           /s/
 
                                              ----------------------------------
                                              Name:
                                              Title:
 
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                                            WR ACQUISITION, INC.
 
                                            By:           /s/
 
                                              ----------------------------------
                                              Name:
                                              Title:
 
                                            AMERICAN PAD & PAPER COMPANY OF
                                            DELAWARE, INC.
 
                                            By:           /s/
 
                                              ----------------------------------
                                              Name:
                                              Title:
 
                                            BANKERS TRUST COMPANY, individually
                                            and as Agent
 
                                            By:           /s/
 
                                              ----------------------------------
                                              Name:
                                              Title:
 
                                            BANKBOSTON, N.A.
 
                                            By:           /s/
 
                                              ----------------------------------
                                              Name:
                                              Title:
 
                                            BANK LEUMI USA
 
                                            By:           /s/
 
                                              ----------------------------------
                                              Name:
                                              Title:
 
                                        3
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                                            THE BANK OF NEW YORK
 
                                            By:           /s/
 
                                              ----------------------------------
                                              Name:
                                              Title:
 
                                            THE BANK OF NOVA SCOTIA
 
                                            By:           /s/
 
                                              ----------------------------------
                                              Name:
                                              Title:
 
                                            BANK OF SCOTLAND
 
                                            By:           /s/
 
                                              ----------------------------------
                                              Name:
                                              Title:
 
                                            BANK OF TOKYO-MITSUBISHI TRUST
                                            COMPANY
 
                                            By:           /s/
 
                                              ----------------------------------
                                              Name:
                                              Title:
 
                                            BANK ONE TEXAS
 
                                            By:           /s/
 
                                              ----------------------------------
                                              Name:
                                              Title:
 
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                                            BANK POLSKA KASA OPIEKI, S.A.
 
                                            By:           /s/
 
                                              ----------------------------------
                                              Name:
                                              Title:
 
                                            CIBC INC.
 
                                            By:           /s/
 
                                              ----------------------------------
                                              Name:
                                              Title:
 
                                            THE LONG-TERM CREDIT BANK OF
                                            JAPAN, LIMITED, NEW YORK BRANCH
 
                                            By:           /s/
 
                                              ----------------------------------
                                              Name:
                                              Title:
 
                                            SOCIETE GENERALE
 
                                            By:           /s/
 
                                              ----------------------------------
                                              Name:
                                              Title:
 
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