<PAGE>
                                                                    EXHIBIT 10.6

 
                               TWELFTH AMENDMENT
                               -----------------
                                       TO
                                       --
                                CREDIT AGREEMENT
                                ----------------

     This Twelfth Amendment to Credit Agreement (this "Amendment") is entered
into effective as of the 16th day of April, 1998, by and between Bank of America
Texas, N.A. (the "Bank") and Stevens International, Inc., formerly known as
Stevens Graphics Corporation, a Delaware corporation (the "Borrower"), and PMC
Liquidation, Inc. and Printing and Packaging Equipment Finance Corporation
(individually a "Guarantor" and together, the "Guarantors").

     Borrower is the surviving corporation of the several mergers between
Borrower, on the one hand, and each of Zerand-Bernal Group, Inc., a Delaware
corporation, Hamilton-Stevens Group, Inc., a Delaware corporation, and Stevens
Securities Systems International, Inc., a Delaware corporation.  Each of the
mergers is evidenced by the respective Certificate of Ownership and Merger,
dated December 21, 1995, signed by the Borrower, and filed with the Office of
the Secretary of State of the State of Delaware on December 22, 1995.

                                   REFERENCE:
                                   ----------

     Reference is made to the Credit Agreement dated as of May 16, 1995 by and
between Bank and Borrower, as amended by the following (as amended, including
all prior amendments described below, the "Credit Agreement"):

          (a) that certain First Amendment to Credit Agreement entered into
     effective as of August 15, 1995;

          (b) that certain Second Amendment to Credit Agreement entered into
     effective as of December 29, 1995;

          (c) that certain Third Amendment to Credit Agreement entered into
     effective as of May 13, 1996;

          (d) that certain Agreement and Fourth Amendment dated as December 31,
     1996 (the "Forbearance Agreement");

          (e) that certain First Amendment to Agreement and Fourth Amendment to
     Credit Agreement dated as of February 28, 1997;

          (f) that certain Second Amendment to Agreement and Fourth Amendment to
     Credit Agreement dated as of March 17, 1997;

          (g) that certain Third Amendment to Agreement and Fourth Amendment to
     Credit Agreement dated as of May 1, 1997;

          (h) that certain Fourth Amendment to Agreement and Fourth Amendment to
     Credit Agreement dated as of July 1, 1997 (the "Fourth Forbearance
     Amendment");

TWELFTH AMENDMENT - Page 1
<PAGE>
 
          (i) that certain Fifth Amendment to Credit Agreement dated as of July
     31, 1997 (the "Fifth Amendment");

          (j) that certain Sixth Amendment to Credit Agreement dated as of
     August 28, 1997 (the "Sixth Amendment");

          (k) that certain Seventh Amendment to Credit Agreement dated as of
     December 31, 1997 (the "Seventh Amendment");

          (l)  that certain Eighth Amendment to Credit Agreement dated as of
     January 23, 1998 (the "Eighth Amendment");

          (m) that certain Ninth Amendment to Credit Agreement dated as of
     February 6, 1998 (the "Ninth Amendment");

          (n) that certain Tenth Amendment to Credit Agreement dated as of
     February 28, 1998 (the "Tenth Amendment"); and
 
          (o) that certain Eleventh Amendment to Credit Agreement dated as of
     March 31, 1998 (the "Eleventh Amendment").


                                   RECITALS:
                                   ---------

     a.   Defaults (the "Existing Defaults") have occurred under the Credit
Agreement and the Loan Documents by reason of the following acts or omissions:

          (1) Violation of Section 11.12 of the Credit Agreement (failure to
     comply with financial covenants), based upon non-compliance with Article
     9.1 for the period ending March 31, 1998 (Debt to Tangible Net Worth
     Ratio);

          (2) Violation of Section 11.12 of the Credit Agreement (failure to
     comply with financial covenants) based upon non-compliance with Article 9.3
     for the period ending March 31, 1998 (Debt Coverage Ratio);

          (3) Violation of Section 11.13 of the Credit Agreement (other breaches
     under Credit Agreement) based upon non-compliance with Article 8.2(b) for
     the period ending March 31, 1998 (Quarterly Report on Form 10-Q and
     Compliance Certificate);

          (4) Violation of Section 11.13 of the Credit Agreement (other breaches
     under Credit Agreement) based upon non-compliance with Article 8.2(b) for
     the period ending December 31, 1997 (Compliance Certificate) and with
     Article 8.2(s) for the period ending March 31, 1998 (Weekly Cash Forecast);

     b.   As of the date hereof, the Existing Defaults remain uncured.


TWELFTH AMENDMENT - Page 2
<PAGE>
 
     c.   Borrower has requested that Bank waive the above noticed Events of
Default under the Credit Agreement and the Loan Documents.

     d.   Borrower has requested Bank's waiver to permit Borrower the
opportunity to consummate the sale of its Zerand Division.

     e.   Bank will waive the Existing Defaults, as requested above by Borrower,
subject to the terms and conditions of this Agreement including, without
limitation, the amendments to the Credit Agreement set forth herein.

                             AFFIRMATION OF FACTS:
                             ---------------------

     Bank and Borrower affirm the following facts:

          (a) During 1996, Borrower defaulted under its obligations under the
     Credit Agreement.  As a result of such defaults, Borrower requested that
     Bank restructure its agreements with Borrower and reported to Bank that
     Borrower had decided to sell its Zerand Division to provide capital to
     reduce its outstanding debt if Borrower could obtain the agreement of the
     holders of the Subordinated Debt to a restructure of Borrower's obligations
     to such holders.  Borrower also requested that Bank agree to forbear from
     the exercise of its rights and remedies under the Credit Agreement to allow
     Borrower time to restructure its debt with the holders of the Subordinated
     Debt; and Bank agreed to forbear for a limited period of time to allow
     Borrower to negotiate with the holders of the Subordinated Debt.

          (b) As of December 31, 1996, Bank and Borrower entered into the
     Forbearance Agreement detailing the terms and conditions of Bank's
     agreement to temporarily forbear from the pursuit of its rights and
     remedies.  Borrower was unable to obtain the agreement of the holders of
     the Subordinated Debt to a restructure acceptable to Borrower during the
     Bank's agreed upon period of forbearance under the Forbearance Agreement
     and from time to time requested that Bank extend its forbearance period (as
     extended from time to time including through the term of the Fourth
     Forbearance Amendment, the "Forbearance Period") to allow Borrower time to
     continue its negotiations with the holders of the Subordinated Debt.  Bank
     agreed to four extensions of the such Forbearance Period, but notified
     Borrower that Bank would not extend the Forbearance Period beyond July,
     1997.

          (c) During the Forbearance Period, Borrower negotiated with the
     holders of the Subordinated Debt and proposed to the holders of the
     Subordinated Debt that Borrower sell among other assets one of its
     divisions and retire Borrower's debt to the Bank in full by December 31,
     1997.  After the holders of the Subordinated Debt agreed in principal with
     Borrower's proposal Borrower requested that Bank agree to restructure its
     agreements with Borrower in accordance with the proposals made to the
     holders of the Subordinated Debt.  After continued negotiations among Bank,
     Borrower and the holders of the Subordinated Debt, Bank agreed to waive its
     then existing defaults and modified its agreements with Borrower in
     accordance with the Fifth Amendment.  The Fifth


TWELFTH AMENDMENT - Page 3
<PAGE>
 
     Amendment and the documents executed in connection therewith are herein
     called the "Modification Documents."

          (d) In early December, 1997, Borrower reported to Bank that it had
     reached an agreement in principal to sell one of its divisions, but
     requested (the "Early December Request") that rather than complying with
     the terms of the Modification Documents, Borrower be allowed to use the
     majority of the net proceeds of such sale to retire the Subordinated Debt
     rather than to retire the debt of Borrower to Bank.  Bank would not agree
     to the use of its collateral to retire indebtedness to others in direct
     contradiction of the terms of the Modification Documents and the Credit
     Agreement.  Borrower then proposed that in lieu of the Early December
     Request (i) the proceeds of Bank's collateral, including without limitation
     all net proceeds of the sale of such division, be applied to retire the
     debt of Borrower to Bank in accordance with the terms of the Credit
     Agreement and related loan documents, and (ii) that the maturity of
     Borrower's obligations to Bank be extended as set forth herein.  Borrower
     acknowledges and agrees that Bank had no duty to agree to any modification
     of the existing agreements between Borrower and Bank.

          (e) Borrower and Bank have entered into the Sixth Amendment, the
     Seventh Amendment, the Eighth Amendment, the Ninth Amendment, the Tenth
     Amendment, and the Eleventh Amendment and now that Borrower has entered
     into an agreement in principle with respect to the sale of Borrower's
     Zerand division, the net proceeds of which will be paid to Bank, Borrower
     has requested that Bank again extend the credit facility evidenced by the
     Credit Agreement until April 30, 1998.

          (f) Borrower acknowledges, agrees and represents and warrants to Bank
     that during all negotiations with Bank, Borrower has been represented by
     competent legal counsel and has consulted with such other professionals as
     it has deemed prudent with respect to its agreements with Bank and all
     modifications thereto and that Borrower has made its decisions based upon
     advice from its legal counsel and other professional advisors without any
     advice from Bank or Bank's representatives or counsel.  Borrower further
     acknowledges, agrees and represents and warrants to Bank that without any
     requirement therefor by Bank, all decisions to sell any of Borrower's
     assets were made solely by Borrower based upon its business judgment and
     upon the advice of legal counsel and other professionals as being in the
     best interests of Borrower to give Borrower the greatest opportunity to
     return to a profitable operation and to retire its obligations to its
     lenders and other creditors.

          (g) Bank and Borrower have agreed that upon the terms and subject in
     all respects to the conditions set forth herein to again amend certain
     existing terms of the Credit Agreement.

                                  AGREEMENTS:
                                  -----------

     NOW, THEREFORE, in consideration of the premises and the mutual covenants
herein contained, and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereto agree as
follows:


TWELFTH AMENDMENT - Page 4
<PAGE>
 
            1.  AMENDMENTS TO CREDIT AGREEMENT AND AGREEMENT TO PAY
            -------------------------------------------------------
                  APPRAISAL AND ENVIRONMENTAL AUDIT EXPENSES
                  ------------------------------------------

     1.1  Article 1 of the Credit Agreement is hereby amended to add the
following definition:


     1.2  The definition of the term Borrowing Base Advance Cap in Article 1 of
the Credit Agreement is hereby restated in its entirety to read as follows:

          The term "Borrowing Base Advance Cap" means the following, as
     determined by reference to the periods of time indicated below:

          (a) at any time prior to the sale of the Zerand Division and the
     Bank's receipt of the proceeds of such sale, an amount equal to the lesser
     of:

              (1)  $11,500,000.00; or

              (2)  the sum of:

                   (i)   80% of the amount of Eligible Accounts; plus

                   (ii)  the lesser of:

                         (A)  $2,750,000.00, or

                         (B)  25% of the amount of Eligible Inventory; plus

                   (iii) $7,837,000.00; and

          (b) at any time after the sale of the Zerand Division and the Bank's
     receipt of the proceeds of such sale, an amount equal to the lesser of:

              (1)  $2,000,000.00; or

              (2)  the sum of:

                   (i)   80% of the amount of Eligible Accounts; plus

                   (ii)  the lesser of:

                         (A)  $1,750,000.00, or

                         (B) 25% of the amount of Eligible Inventory; plus

                   (iii) $500,000.00.


TWELFTH AMENDMENT - Page 5
<PAGE>
 
     1.3  The definition of the term "Note" in Article 1 of the Credit Agreement
is amended to mean the Note as defined in the Fifth Amendment as further amended
by that certain Seventh Note and Liens Modification Agreement of even date
herewith (the "Note Modification Agreement").

     1.4. Section 2.1. of the Credit Agreement is hereby restated in its
entirety to read as follows:

              (a) During the availability period described below, the Bank will
     provide the Revolving Line of Credit to the Borrower. The Borrower agrees
     that it will use the proceeds of each advance under the Revolving Line of
     Credit only for working capital purposes and for capital expenditures
     permitted by Section 9.4 of the Credit Agreement. The amount of the
     Revolving Line of Credit available for Letters of Credit and advances
     outstanding at any time including amounts paid under any Letter of Credit
     is an amount of up to the lesser of (i) $11,500,000.00, prior to the sale
     of the Zerand Division, and $2,000,000.00 after the sale of the Zerand
     Division, or (ii) the Borrowing Base Advance Cap (the "Commitment") .

              (b) The Borrower agrees not to permit the outstanding principal
     balance of the Revolving Line of Credit plus the amount of all then
     outstanding Letters of Credit, including amounts drawn on letters of credit
     and not yet reimbursed, to exceed the lesser of (i) $11,500,000.00, prior
     to the sale of the Zerand Division, and $2,000,000.00 after the sale of the
     Zerand Division, or (ii) the Borrowing Base Advance Cap. If such amounts
     outstanding exceed the foregoing limitations, the Borrower will immediately
     pay the excess to the Bank upon the Bank's demand. The Bank may apply
     payments received from the Borrower under this Section to the obligations
     of the Borrower to the Bank in the order and the manner as the Bank, in its
     discretion, may determine.

     1.5  The term Expiration Date contained in Section 2.2 of the Credit
Agreement, is amended to mean the earlier to occur of (i) April 30, 1998, or
(ii) the date the sale of Borrower's Zerand Division occurs.

     1.6  Article 3 of the Credit Agreement, Fees and Expenses, is hereby
amended by the addition of the following provision:

          3.10 Additional Loan Restructure Fees:  Borrower agrees to pay Bank
$4,500.00 on the date this Amendment is executed, as a loan restructuring and
commitment fee for extending the Expiration Date beyond April 15, 1998.

     1.7  Borrower agrees to promptly pay to Bank upon demand therefor all costs
of Bank's obtaining appraisals of the collateral held by Bank to secure
Borrower's obligations to Bank and all costs of an environmental audit of all
real estate that is included in such collateral.

     1.8  Except as amended hereby, the Credit Agreement shall continue in full
force and effect in accordance with its provisions.


TWELFTH AMENDMENT - Page 6
<PAGE>
 
                            2. CONDITIONS PRECEDENT
                            -----------------------

     The effectiveness of this Amendment is expressly conditioned upon delivery
to Bank of each of the following, each document to be in form and content
acceptable to Bank in its sole discretion:

     2.1  Corporate Documents.  Appropriate corporate documentation, including
without limitation resolutions of the Executive Committee of the Board of
Directors of Borrower approving the execution, delivery and performance of (a)
this Amendment and all documents executed in connection herewith, and (b) the
Letter of Intent with respect to the sale of the above referenced division and
the proposed sale pursuant thereto.

     2.2  Other Loan Documents.  The following loan documents:

          (a) Notice of Final Agreement. A fully executed Notice of Final
     Agreement in compliance with Section 26.02 of the Texas Business and
     Commerce Code.

          (b) Note Modification Agreement. A fully executed Note Modification
     Agreement.

          (c) Master Amendment to Security Documents. A fully executed Tenth
     Master Amendment to Security Documents.

     2.3  Legal Opinion.  An opinion of legal counsel to Borrower and
Guarantors.

     2.4  Amendment to Intercreditor Agreement.  A fully executed Multi-party
Agreement entered into with respect to the Intercreditor Agreement.

     2.5  Intercreditor Agreement With Paul Stevens.  A fully executed copy of
an Intercreditor Agreement with Paul Stevens and Borrower whereby Paul Stevens
and the Borrower agree that no payments will be made upon any indebtedness of
Borrower to Paul Stevens until May 2, 1998.

     2.6  Other Documentation.  Such other documents as the Bank may request.

                               3.  MISCELLANEOUS.
                               ------------------

     3.1  Representations.  Borrower represents and warrants that the execution,
delivery and performance by Borrower of this Amendment and the Credit Agreement
as amended hereby have been duly authorized by all necessary corporate action
and that this Amendment and the Credit Agreement as amended hereby are legal,
valid and binding obligations of Borrower enforceable against Borrower in
accordance with their terms, except to the extent that such enforcement may be
limited by applicable bankruptcy, insolvency and other similar laws affecting
creditors' rights generally, or by general principles of equity limiting the
availability of certain remedies.


TWELFTH AMENDMENT - Page 7
<PAGE>
 
     3.2  Ratifications.  The terms and provisions set forth in this Amendment
shall modify and supersede all inconsistent terms and provisions set forth in
the Credit Agreement, and, except as expressly modified and superseded by this
Amendment, the terms and provisions of the Credit Agreement are ratified and
confirmed and shall continue in full force and effect.  Borrower and Bank agree
that the Credit Agreement as amended hereby shall continue to be legal, valid,
binding and enforceable in accordance with its terms and that the amounts
outstanding under the Revolving Line of Credit are obligations under the Credit
Agreement and are secured by the Collateral described in Article 4 of the Credit
Agreement.

     3.3  Governing Law.  This Amendment shall be governed by and construed in
accordance with the laws of the State of Texas.

     3.4  Counterparts.  This Amendment may be executed in any number of
counterparts, all of which taken together shall constitute one and the same
instrument and any of the parties hereto may execute this Amendment by signing
any such counterpart.

     3.5  Definitions.  Capitalized terms used in this Amendment and not
otherwise defined in this Amendment shall have the meanings given them in the
Credit Agreement.

     3.6  WAIVER OF JURY TRIAL.  BORROWER, EACH OF THE UNDERSIGNED GUARANTORS
(THE "GUARANTORS") AND THE BANK EACH WAIVE THEIR RESPECTIVE RIGHTS TO A TRIAL BY
JURY OF ANY CLAIM OR CAUSE OF ACTION BASED UPON OR ARISING OUT OF OR RELATED TO
THIS AMENDMENT, THE CREDIT AGREEMENT, THE OTHER LOAN DOCUMENTS, OR THE
TRANSACTIONS CONTEMPLATED HEREBY OR THEREBY, IN ANY ACTION, PROCEEDING OR OTHER
LITIGATION OF ANY TYPE BROUGHT BY ANY OF THE PARTIES AGAINST ANY OTHER PARTY OR
ANY PARTICIPANT OR ASSIGNEE, WHETHER WITH RESPECT TO CONTRACT CLAIMS, TORT
CLAIMS, OR OTHERWISE.  BORROWER, EACH OF THE GUARANTORS AND BANK EACH AGREE THAT
ANY SUCH CLAIM OR CAUSE OF ACTION SHALL BE TRIED BY A COURT TRIAL WITHOUT A
JURY.  WITHOUT LIMITING THE FOREGOING, THE PARTIES FURTHER AGREE THAT THEIR
RESPECTIVE RIGHT TO A TRIAL BY JURY IS WAIVED BY OPERATION OF THIS SECTION AS TO
ANY ACTION, COUNTERCLAIM OR OTHER PROCEEDING WHICH SEEKS, IN WHOLE OR IN PART,
TO CHALLENGE THE VALIDITY OR ENFORCEABILITY OF THIS AMENDMENT, THE CREDIT
AGREEMENT OR THE OTHER LOAN DOCUMENTS OR ANY PROVISION HEREOF OR THEREOF.  THIS
WAIVER SHALL APPLY TO ANY SUBSEQUENT AMENDMENTS, RENEWALS, SUPPLEMENTS OR
MODIFICATIONS TO THE CREDIT AGREEMENT AND THE OTHER LOAN DOCUMENTS.

     3.7  RELEASES.  BORROWER AND EACH GUARANTOR FULLY, COMPLETELY AND FOREVER
RELEASE THE BANK AND ITS PRESENT AND FORMER AFFILIATES, SUBSIDIARIES, AGENTS,
ATTORNEYS, APPRAISERS, CONSULTANTS, EMPLOYEES, OFFICERS, DIRECTORS,
STOCKHOLDERS, SUCCESSORS AND ASSIGNS ("OTHER RELEASED PARTIES") FROM ANY


TWELFTH AMENDMENT - Page 8
<PAGE>
 
DEMANDS, CLAIMS AND CAUSES OF ACTION EXISTING AS OF THE DATE HEREOF, WHETHER
KNOWN OR UNKNOWN, WHETHER FOR KNOWN OR UNKNOWN DAMAGES OR ANY OTHER RELIEF,
INCLUDING, BUT NOT LIMITED TO, DEMANDS, CLAIMS, CAUSES OF ACTION OR DAMAGES
DIRECTLY OR INDIRECTLY RELATING TO OR BASED ON:

          (a) ANY AND ALL TRANSACTIONS RELATING TO THE CREDIT AGREEMENT OR ANY
OF THE OTHER LOAN DOCUMENTS AS AMENDED FROM TIME TO TIME, INCLUDING, WITHOUT
LIMITATION, ANY LOSS, EXPENSES AND/OR DETRIMENT OF ANY KIND OR CHARACTER GROWING
OUT OF OR IN ANY WAY RESULTING FROM THE ACTS OR OMISSIONS OF BANK OR THE OTHER
RELEASED PARTIES;

          (b) ANY LOSS, COST OR DAMAGE IN CONNECTION WITH ANY BREACH OF
FIDUCIARY DUTY, FRAUD, BREACH OF A DUTY OF GOOD FAITH AND FAIR DEALING,  BREACH
OF CONFIDENCE, BREACH OF FUNDING COMMITMENT, IMPAIRMENT OF COLLATERAL,
VIOLATIONS OF THE BANK TYING ACT (12 U.S.C. (S) 1971, ET SEQ.), UNDUE INFLUENCE,
DURESS, ECONOMIC COERCION, CONFLICT OF INTERESTS, NEGLIGENCE, BAD FAITH,
MALPRACTICE, INTENTIONAL OR NEGLIGENT INFLICTION OF MENTAL DISTRESS, TORTIOUS
INTERFERENCE WITH CONTRACTUAL RELATIONS, TORTIOUS INTERFERENCE WITH CORPORATE
GOVERNANCE OR PROSPECTIVE BUSINESS ADVANTAGE, BREACH OF CONTRACT, DECEPTIVE
TRADE PRACTICES, LIBEL, SLANDER, OR CONSPIRACY; AND

          (c) ANY OTHER CLAIM BASED ON CONTRACT, TORT, COMMON LAW, OR ANY RIGHT
CREATED BY A STATUTE OR REGULATION PROMULGATED BY ANY GOVERNMENT AGENCY.

     THE ABOVE LISTING OF DEMANDS, CLAIMS AND CAUSES OF ACTION RELEASED IS NOT
EXCLUSIVE OR EXHAUSTIVE.  IT IS THE EXPRESS INTENTION OF THE BORROWER AND
GUARANTORS TO RELEASE AND FORGIVE THE BANK OF ALL DEMANDS, CLAIMS AND CAUSES OF
ACTION FROM THE PAST AND HAVE A FRESH START FROM THIS DAY FORWARD.  BORROWER AND
EACH GUARANTOR, ON BEHALF OF THEMSELVES AND THEIR SUCCESSORS AND ASSIGNS,
COVENANT AND AGREE NOT TO SUE, INSTITUTE, OR COOPERATE IN THE INSTITUTION,
COMMENCEMENT, FILING, OR PROSECUTION OF ANY SUIT, ADMINISTRATIVE PROCEEDING,
DEMAND, CLAIM OR CAUSE OF ACTION ARISING FROM ANY ASPECT OF THE CREDIT AGREEMENT
OR ANY OTHER LOAN DOCUMENTS, AS AMENDED, WHETHER ASSERTED INDIVIDUALLY OR
DERIVATIVELY OR IN ANY CAPACITY AGAINST BANK OR THE OTHER RELEASED PARTIES.
FURTHERMORE, BORROWER AND EACH GUARANTOR REPRESENT AND WARRANT THAT THEY HAVE
NOT ASSIGNED, AND WILL NOT HEREAFTER ASSIGN, ANY OF THEIR ALLEGED CLAIMS OR
CAUSES OF ACTION, OF ANY KIND OR NATURE WHATSOEVER, AGAINST THE BANK OR THE
OTHER RELEASED PARTIES TO ANY PERSON OR


TWELFTH AMENDMENT - Page 9
<PAGE>
 
ENTITY, SO THAT NO OTHER PARTY IS IN A POSITION TO ASSERT ANY SUCH CLAIM OR
CAUSE OF ACTION.

     3.8    Ratification of Security Documents. Borrower and each Guarantor
agree that those certain security documents (as heretofore amended, the
"Security Documents"), which are more fully described in Exhibit A attached to
that certain Master Amendment to Security Documents, dated May 16, 1995,
executed by Guarantors and Borrower in favor of the Bank, are in full force and
effect as of the date hereof. Borrower and each Guarantor hereby ratify the
rights, titles, liens and security interests under the Security Documents in
favor of Bank.

     3.9    Successors and Assigns. This Amendment, the Credit Agreement and all
documents executed in connection with or as security for the Credit Agreement
(the "Security Documents") are binding on the Borrower's and the Bank's
successors and assignees. The Borrower agrees that it may not assign this
Amendment without the Bank's prior consent. The Bank may sell participations in
or assign this Amendment, the Credit Agreement and the Security Documents, and
may exchange financial information about the Borrower with actual or potential
participants or assignees, provided that such potential participants and
assignees agree to keep non-public information regarding Borrower confidential.
If a participation is sold or the loan is assigned, the purchaser will have the
right of set-off against the Borrower.

     3.10.  Ratification of Guaranties. The Guarantors agree that that certain
Business Loan Continuing Guaranty, dated May 16, 1995 (the "Guaranty"), executed
by the Guarantors in favor of the Bank, shall remain in full force and effect
and shall continue to be the legal, valid and binding obligation of the
Guarantors enforceable against Guarantors in accordance with its terms.
Furthermore, the Guarantors hereby agree and acknowledge that (a) the
obligations, indebtedness and liabilities arising in connection with the Credit
Agreement as amended by this Amendment constitute "Debt," as such term is
defined in the Guaranty, (b) as of the date hereof, the Guaranty is not subject
to any claims, defenses or offsets, (c) nothing contained in the Credit
Agreement or this Amendment shall adversely affect any right or remedy of Bank
under the Guaranty, and (d) the execution and delivery of this Amendment shall
in no way reduce, impair or discharge any obligations of the Guarantors pursuant
to the Guaranty.

     3.11.  NO DUTY TO EXTEND.  BORROWER AND THE UNDERSIGNED GUARANTORS
ACKNOWLEDGE AND AGREE THAT BANK HAS ABSOLUTELY NO DUTY OR OBLIGATION OF ANY
NATURE TO AGAIN EXTEND THE EXPIRATION DATE OR TO AGREE TO ANY OTHER AMENDMENT TO
THE CREDIT AGREEMENT.

     3.12.  Year 2000.  Borrower acknowledges that it has received a copy of the
brochure prepared by the Bank entitled "On Turning 00" and that it has reviewed
this material and is aware of the possible impact of the year 2000 problem (that
is, the risk that computer applications may not be able to properly perform
date-sensitive functions after December 31, 1999) upon its computer applications
and on-going business.  Borrower represents that any corrective action necessary
will be taken and that Borrower does not believe the year 2000 problem will
result in a material adverse change in Borrower's business condition (financial
or otherwise), operations, properties or prospects, or ability to repay the
credit.


TWELFTH AMENDMENT - Page 10
<PAGE>
 
     IN WITNESS WHEREOF, Borrower and Bank have caused this Amendment to be duly
executed as of the day and year first above written.

BANK OF AMERICA TEXAS, N.A.            STEVENS INTERNATIONAL, INC.,
                                       formerly known as Stevens Graphics
                                       Corporation



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


TWELFTH AMENDMENT - Page 11
<PAGE>
 
     Executed for the purposes of acknowledging and agreeing to the provisions
of Sections 3.6, 3.7, 3.8, 3.9, 3.10 and 3.11 hereof.

                                    GUARANTORS

                                    PMC LIQUIDATION, INC.,
                                    formerly known as Post Machinery
                                    Company, Inc.
 


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


                                    PRINTING & PACKAGING EQUIPMENT
                                         FINANCE CORPORATION



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



TWELFTH AMENDMENT - Page 12