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                                                                    EXHIBIT 4.18


                                FOURTH AMENDMENT


         FOURTH AMENDMENT (this "Amendment"), dated as of April 6, 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.


                              W I T N E S S E T H:


         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"); 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.    Section 8.10 of the Credit Agreement is hereby amended to read in
its entirety as follows:

               8.10 Minimum Consolidated EBITDA. The Borrower will not permit 
     Consolidated EBITDA (i) for the fiscal quarter ending March 31, 1998, to be
     less than $11,300,000, (ii) for the two fiscal quarters ending June 30,
     1998 (taken as one accounting period), to be less than $28,000,000, (iii)
     for the three fiscal quarters ending September 30, 1998 (taken as one
     accounting period), to be less than $48,000,000, (iv) for the fiscal year
     ending December 31, 1998, to be less than $72,000,000 and (v) for any Test
     Period ending on or after March 31, 1999, to be less than $75,000,000.

         2.    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.

         3.    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;


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         4.    This Amendment is limited as specified and shall not constitute a
modification, acceptance or waiver of any other provision of the Credit
Agreement or any other Credit Document.

         5.    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.


               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.

                                      * * *



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         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:
                                          ------------------------------------
                                          Name:
                                          Title:



                                       WR ACQUISITION, INC.



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



                                       AMERICAN PAD & PAPER COMPANY OF
                                       DELAWARE, INC.



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


                                       BANKERS TRUST COMPANY, individually
                                         and as Agent


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



                                       3
<PAGE>   4
                                       ABN AMRO BANK



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



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



                                        BANK LEUMI TRUST CO. OF NEW YORK



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



                                       THE BANK OF NEW YORK



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



                                       THE BANK OF NOVA SCOTIA
 


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



                                       4

<PAGE>   5

                                        BANK OF SCOTLAND



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



                                       BANK OF TOKYO-MITSUBISHI TRUST COMPANY



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



                                       BANK ONE TEXAS



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



                                       BANQUE PARIBAS



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


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




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                                       CHRISTIANIA BANK OG KREDITKASSE,
                                         NEW YORK BRANCH



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



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



                                       CIBC INC.



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



                                       BANKBOSTON, N.A.



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



                                       GUARANTY FEDERAL BANK, F.S.B.



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



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<PAGE>   7

                                       THE INDUSTRIAL BANK OF JAPAN, 
                                         LIMITED



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



                                       THE LONG-TERM CREDIT BANK OF 
                                         JAPAN, LIMITED, NEW YORK BRANCH



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



                                       SANWA BUSINESS CREDIT
                                         CORPORATION



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



                                       SOCIETE GENERALE



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



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<PAGE>   8

                                       LEHMAN COMMERCIAL PAPER, INC.



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




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