<PAGE>

                                                                  Exhibit 10(c)

October 27, 1998

VIA Facsimile and U.S. Mail

To the Holders of
     6% Convertible Preferred Stock
     of Interleaf, Inc.

Re:  6% Convertible Preferred Stock

Gentlemen:

Reference is made to the Preferred Stock Investment Agreement, dated as of
September 30, 1997 (the "Investment Agreement"), between Interleaf, Inc.
("Interleaf") and you pursuant to which you acquired such number of shares of 6%
Convertible Preferred Stock of Interleaf ("6% Preferred") as set forth beside
your name below.

Interleaf and you hereby agree to consummate the transactions set forth on the
Term Sheet attached as Exhibit A hereto on the terms set forth therein.

Interleaf's obligations to consummate such transactions are contingent upon
Interleaf obtaining financing from third parties in at least the aggregate
amount required to fund the initial redemption as set forth in the Term Sheet.
However, in this regard, Interleaf represents that it has obtained financing
commitments in an aggregate amount sufficient to fund such initial redemption,
subject only to the requirement that Interleaf obtain the agreement of the
holders of at least 75% of the 6% Preferred currently outstanding to consummate
the transactions set forth on the Term Sheet.

Interleaf's and your obligations to consummate the transactions set forth on the
Term Sheet shall terminate unless (i) Interleaf receives executed counterparts
hereof from the holders of at least 75% of the 6% Preferred currently
outstanding on or before November 6, 1998, and (ii) the transactions
contemplated herein are consummated on or before the earlier to occur of (a) the
date which is ten (10) days from the day on which Interleaf receives executed
counterparts hereof from the holders of at least 75% of the 6% Preferred
currently outstanding, or (b) November 20, 1998; provided, that Interleaf has
the right to extend each of these dates one time for a period of up to three (3)
business days as necessary for ministerial purposes.

This Letter Agreement is being executed by you subject to and conditioned as
follows: (i) the final agreements and related documents will in all respects be
subject to your approval and will contain the same terms and conditions
described herein, and (ii) in the event that Interleaf offers any other holder
of 6% Preferred, whether or not a signatory to a counterpart of this letter
agreement, terms and conditions different from those contained herein, you shall
have the right, but not the obligation, to consummate the transaction upon such
other terms and conditions.



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                                                              Series D Investors
                                                                October 27, 1998
                                                                          Page 2



     If you are in agreement with the foregoing, please sign, date and return
this letter which will constitute our agreement with respect thereto.

                                       Very truly yours,


                                       INTERLEAF, INC.


                                       By:
                                           ---------------------------------
                                           Peter J. Rice, CFO


Agreed and accepted:

<TABLE>
<CAPTION>

                                         Shares of 6% Preferred
                                 ----------------------------------------
                                      Initially           Currently
                                      Purchased               Held
<S>                              <C>                    <C>
Name of Investor
                                        X,000               X,000

</TABLE>

By:
       --------------------------------
Name:
       --------------------------------
Title:
       --------------------------------
Date:
       --------------------------------





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  Exhibit A to Letter Agreement With Holders of 6% Convertible Preferred Stock

                                   TERM SHEET
                                  Amendment to
                      Preferred Stock Investment Agreement
                                       for
                         6% Convertible Preferred Stock
                                       of
                                 Interleaf, Inc.

Initial Redemption: Interleaf shall initially redeem 40% of the Investor's 6%
                    Convertible Preferred Stock at $1,150 per share, inclusive
                    of dividends accrued to date.

Payment:            $1,000 per share will be paid in cash.

                    $ 150 per share will be paid in the form of Interleaf Common
                    Stock, valued at $1.00 per share.

Conversion:         Please indicate your preference:

           / /      The Conversion Price shall be permanently fixed at $1.40 for
                    the remaining 60% of the Investor's 6% Convertible Preferred
                    Stock. Future dividends on shares of 6% Convertible
                    Preferred remaining outstanding after the initial
                    redemption, if any, shall continue to accrue at 6% under
                    original terms. The 6% Convertible Preferred Stock shall be
                    100% convertible immediately and permanently.

                                       OR

           / /      The remaining 60% of the Investor's 6% Convertible Preferred
                    Stock, together with dividends accrued in kind to the date
                    of conversion, shall be immediately converted into Common
                    Stock, using a Conversion Price of $1.10.

Other:              The Preferred Stock Investment Agreement and the 6%
                    Convertible Preferred Stock certificate of designation shall
                    remain in full force and effect under original terms;
                    provided, that (as set forth above) the Conversion Price
                    shall be permanently fixed at $1.40 and all (100%) of the 6%
                    Convertible Preferred Stock that remains outstanding shall
                    be immediately convertible into Common Stock.