<PAGE>
 
                                                                   EXHIBIT 10.31

                               PLEDGE AGREEMENT
                                        
                                        
          THIS PLEDGE AGREEMENT (the "Agreement"), dated November 10, 1997, is
made and entered into by and between PORTACOM WIRELESS, INC., a Delaware
corporation (the "Debtor") and VDC CORPORATION LTD., (the "Secured Party") under
that certain Loan Agreement dated of even date herewith (as it may hereafter
from time to time be restated, amended, modified or supplemented, the "Loan
Agreement") by and between the Debtor and the Secured Party.

          WHEREAS, pursuant to the Loan Agreement, the Secured Party agreed to
provide certain loans to Debtor; and

          WHEREAS, as security for such loans, and as required by the Loan
Agreement, all of the warrants (whether now existing or hereafter acquired) held
by Debtor to purchase common stock of Metromedia Asia Corporation ("MAC") shall
be pledged to the Secured Party in accordance herewith.

          NOW, THEREFORE, intending to be legally bound hereby, the parties
hereto agree as follows:

          1.  Defined Terms.
              ------------- 

              (a)  Except as otherwise expressly provided herein, capitalized
terms used in this Agreement shall have the respective meanings assigned to them
in the Loan Agreement. Where applicable and except as otherwise expressly
provided herein, terms used herein (whether or not capitalized) shall have the
respective meanings assigned to them in the Uniform Commercial Code as enacted
in each applicable jurisdiction and as may be amended from time to time (the
"Code").

              (b)  "Pledged Collateral" shall mean and include the following:
(i) the securities listed on Schedule A attached hereto and made a part hereof,
                             ----------
and all rights and privileges pertaining thereto, including, without limitation,
all securities and additional securities receivable in respect of or in exchange
for such securities, all rights to subscribe for securities incident to or
arising from ownership of such securities, all cash, interest, stock and other
dividends or distributions paid or payable on such securities, and all books and
records pertaining to the foregoing, including, without limitation, all stock
record and transfer books, (ii) any and all other securities hereafter pledged
to the Secured Party to secure the Secured Obligations (as hereinafter defined)
of Debtor, and all rights and privileges pertaining thereto, including, without
limitation, all securities and additional securities receivable in respect of or
in exchange for such securities, all rights to subscribe for securities incident
to or arising from ownership of such securities, all cash, interest, stock and
other dividends or distributions paid or payable on such securities, and all
books and records pertaining to the foregoing, including, without limitation,
all stock record and stock transfer books and (iii) whatever is received when
any of the foregoing is 

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sold, exchanged or otherwise disposed of, including any proceeds as such term is
defined in the Code.

          2.  Grant of Security Interests.
              --------------------------- 

              (a)  Debtor, to secure on a first priority basis, the payment and
performance of all of its indebtedness and other obligations of every nature it
owes under the Loan Agreement, any and all Notes and all of the Other Documents
(the "Secured Obligations"), hereby grants to the Secured Party a security
interest in all of Debtor's now existing and hereafter acquired and/or arising
right, title and interest in, to and under the Pledged Collateral, whether now
or hereafter existing and wherever located.

              (b)  Upon the execution and delivery of this Agreement, Debtor has
delivered to and deposited with the Secured Party in pledge, stock and/or
warrant certificates and any other instruments evidencing the Pledged
Collateral, together with undated stock powers signed in blank by Debtor.

          3.  Further Assurances.
              ------------------ 

             Prior to or concurrently with the execution of this Agreement, and
thereafter at any time and from time to time upon reasonable request of the
Secured Party, Debtor shall execute and deliver to the Secured Party all
financing statements, continuation financing statements, termination statements,
assignments, certificates and documents of title, affidavits, reports, notices,
schedules of account, letters of authority, further pledges, powers of attorney
and all other documents (collectively, the "Security Documents") which the
Secured Party may reasonably request, in form reasonably satisfactory to the
Secured Party, and take such other action which the Secured Party may request,
to perfect and continue perfected and to create and maintain the first priority
status of the Secured Party's security interest in (subject only to Permitted
Liens) the Pledged Collateral and to fully consummate the transactions
contemplated under the Loan Agreement, any and all Notes and this Agreement.
Debtor hereby irrevocably makes, constitutes and appoints the Secured Party (and
any of the Secured Party's officers or employees or agents designated by the
Secured Party) as Debtor's true and lawful attorney with power to sign the name
of Debtor on all or any of the Security Documents which the Secured Party
reasonably determines must be executed, filed, recorded or sent in order to
perfect or continue perfected the Secured Party's security interest in the
Pledged Collateral in the event Debtor fails to so execute such documents upon
Secured Party's request.  Such power, being coupled with an interest, is
irrevocable until all of the Secured Obligations have been indefeasibly paid in
full and have terminated.

          4.  Representations and Warranties.
              ------------------------------ 

             In addition to the representations and warranties of Debtor set
forth in the Loan Agreement which are incorporated herein by reference, Debtor
hereby represents and warrants to the Secured Party as follows:

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              (a)  Debtor has, and will continue to have (or, in the case of
after-acquired Pledged Collateral, at the time Debtor acquires rights in such
Pledged Collateral, will have), title to the Pledged Collateral, free and clear
of all Liens.

              (b)  Debtor owns warrants or other ownership interests of MAC as
set forth in Schedule A hereto.

              (c)  The warrants to purchase shares of common stock constituting
the Pledged Collateral have been duly authorized and validly issued to Debtor
(as set forth on Schedule A hereto), and constitute all of the warrants to
                 ----------
purchase common stock of MAC owned by Debtor.

              (d)  The security interests in the Pledged Collateral granted
hereunder are valid, perfected and of first priority.

              (e)  There are no restrictions upon the transfer of the Pledged
Collateral and Debtor has the power and authority and right to transfer the
Pledged Collateral free of any encumbrances and without obtaining the consent of
any other person. It is acknowledged that a transfer of the Pledged Collateral
by Secured Party following a foreclosure may require compliance with federal and
state securities laws.

              (f)  Debtor has all necessary power to execute, deliver and
perform this Agreement and all necessary action to authorize the execution,
delivery and performance of this Agreement has been properly taken.

              (g)  There are no actions, suits, or proceedings pending or, to
Debtor's best knowledge after due inquiry, threatened against or affecting
Debtor with respect to the Pledged Collateral, at law or in equity or before or
by any commission, board, bureau, agency, department or instrumentality, and
Debtor is not in default with respect to any judgment, writ, injunction, decree,
rule or regulation which would adversely affect Debtor's performance hereunder.

              (h)  This Agreement has been duly executed and delivered and
constitutes the valid and legally binding obligation of Debtor, enforceable in
accordance with its terms, except to the extent that enforceability of this
Agreement may be limited by applicable bankruptcy, insolvency, reorganization,
moratorium or other similar laws affecting the enforceability of creditors'
rights generally or limiting the right of specific performance or by general
equitable principles.

              (i)  Neither the execution and delivery by Debtor of this
Agreement, nor the compliance with the terms and provisions hereof, will violate
any provision of the articles or certificates of incorporation or similar
organizational documents, bylaws or partnership agreement of Debtor or any law
or conflict with or result in a breach of any of the terms, conditions or
provisions of any judgment, order, injunction, decree or ruling of any court or
arbitration tribunal or any governmental authority to which Debtor is subject or
any provision of 

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any material agreement, understanding or arrangement to which Debtor is a party
or by which Debtor is bound.

              (j)  Debtor's principal place of business and chief executive
office is as set forth on the signature page hereto.

          5.  General Covenants.
              ----------------- 

             In addition to any covenants and agreements of Debtor set forth in
the Loan Agreement, the Notes and Other Documents, which are incorporated herein
by this reference, Debtor hereby covenants and agrees as follows:

              (a)  Debtor shall do all reasonable acts that may be necessary and
appropriate to maintain, preserve and protect the Pledged Collateral; Debtor
shall be responsible for the risk of loss of, damage to, or destruction of the
Pledged Collateral owned by Debtor, unless such loss is the result of the gross
negligence or willful misconduct of the Secured Party. Debtor shall notify the
Secured Party in writing ten (10) days prior to any change in either the address
and location of Debtor's chief executive office or the address and location of
Debtor's principal place of business.

              (b)  Debtor shall pay promptly when due all taxes, assessments,
charges and obligations secured by encumbrances and liens now or hereafter
imposed upon or affecting any of the Pledged Collateral, except as otherwise
expressly permitted under the Loan Agreement.

              (c)  Debtor shall appear in and defend any action or proceeding of
which Debtor is aware which could reasonably be expected to affect Debtor's
title to, or the Secured Party's interest in, the Pledged Collateral owned by
Debtor and the proceeds thereof; provided, however, that Debtor may settle such
                                 --------  -------
actions or proceedings with respect to the Pledged Collateral Debtor owns with
the consent of the Secured Party, which consent shall not be unreasonably
withheld or delayed.

              (d)  Debtor shall keep separate, accurate and complete records of
the Pledged Collateral owned by Debtor, disclosing the Secured Party's security
interest hereunder.

              (e)  Debtor shall permit the Secured Party, its officers,
employees and agents at reasonable times and on reasonable prior notice to
inspect all books and records related to the Pledged Collateral.

              (f)  During the term of this Agreement, Debtor shall not sell,
assign, transfer, pledge, grant a security interest, place a lien on or
otherwise dispose of the Pledged Collateral except as permitted under the Loan
Agreement.

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          6.  Other Rights With Respect to Pledged Collateral.
              ----------------------------------------------- 

             In addition to the other rights with respect to the Pledged
Collateral granted to the Secured Party hereunder, at any time and from time to
time, after and during the continuation of an Event of Default, the Secured
Party at its option and at the expense of Debtor, may (a) transfer into its own
name, or into the name of its nominee, all or any part of the Pledged
Collateral, thereafter receiving all dividends, income or other distributions
upon the Pledged Collateral; (b) take control of and manage all or any of the
Pledged Collateral; (c) apply to the payment of any of the Secured Obligations,
whether any be due and payable or not, any moneys, including cash dividends and
income from any Pledged Collateral, now or hereafter in the hands of the Secured
Party or any Affiliate of the Secured Party, on deposit or otherwise, belonging
to Debtor, as the Secured Party, in its sole discretion, shall determine; and
(d) do anything which Debtor is required but fails to do hereunder. The proceeds
of any collection, sale or other disposition of the Pledged Collateral of
Debtor, or any part thereof, shall, after the Secured Party has made all
deductions of expenses, including but not limited to reasonable attorneys' fees
and other expenses incurred in connection with repossession, collection, sale or
disposition of such Pledged Collateral or in connection with the enforcement of
the Secured Party's rights with respect to the Pledged Collateral in any
insolvency, bankruptcy or reorganization proceedings, be applied against the
Secured Obligations, whether or not all the same be then due and payable, in
such manner and order as set forth in the Loan Agreement.

          7.  Additional Remedies Upon Event of Default.
              ----------------------------------------- 

             Upon the occurrence of any Event of Default and while such Event of
Default shall be continuing, the Secured Party shall have, in addition to all
rights and remedies of a secured party under the Code or other applicable Law,
and in addition to its rights under Section 6 above and under the Loan
Agreement, the Notes and the Other Documents, the following rights and remedies:

              (a)  The Secured Party may, after ten (10) days' advance notice to
Debtor, sell, assign, give an option or options to purchase or otherwise dispose
of the Pledged Collateral or any part thereof at public or private sale, at any
of the Secured Party's offices or elsewhere, for cash, on credit or for future
delivery, and upon such other terms as the Secured Party may deem commercially
reasonable. Debtor agrees that ten (10) days' advance notice of the time and
place of any public sale or the time after which any private sale is to be made
shall constitute reasonable notification. The Secured Party shall not be
obligated to make any sale of Pledged Collateral regardless of notice of sale
having been given. The Secured Party may adjourn any public or private sale from
time to time by announcement at the time and place fixed therefor, and such sale
may, without further notice, be made at the time and place to which it was so
adjourned. Debtor recognizes that the Secured Party may be compelled to resort
to one or more private sales of the Pledged Collateral to a restricted group of
purchasers who will be obliged to agree, among other things, to acquire such
securities for its own account for investment and not with a view to the
distribution or resale thereof. Debtor acknowledges and agrees that any such
private sale may result in prices and other terms less favorable than if such
sale were a public sale and, notwithstanding such circumstances, agrees that any
such private sale 

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shall be deemed to have been made in a commercially reasonable manner. The
Secured Party shall be under no obligation to delay sale of any of the Pledged
Collateral for the period of time necessary to permit Debtor to register such
securities for public sale under the Securities Act of 1933, as amended, or
under applicable state securities laws, even if Debtor would agree to do so.

              (b)  The proceeds of any collection, sale or other disposition of
the Pledged Collateral of Debtor, or any part thereof, shall, after the Secured
Party has made all deductions of expenses, including but not limited to
reasonable attorneys' fees and other expenses incurred in connection with
repossession, collection, sale or disposition of such Pledged Collateral or in
connection with the enforcement of the Secured Party's rights with respect to
the Pledged Collateral in any insolvency, bankruptcy or reorganization
proceedings, be applied against the Secured Obligations, whether or not all the
same be then due and payable, in such manner and order as set forth in the Loan
Agreement.

          8.  Secured Party's Duties.
              ---------------------- 

             The powers conferred on the Secured Party hereunder are solely to
protect its interest in the Pledged Collateral and shall not impose any duty
upon it to exercise any such powers.  Except for the safe custody of any Pledged
Collateral in its possession and the accounting for moneys actually received by
it hereunder, the Secured Party shall have no duty as to any Pledged Collateral
or as to the taking of any necessary steps to preserve rights against prior
parties or any other rights pertaining to any Pledged Collateral.

          9.  No Waiver; Cumulative Remedies.
              ------------------------------ 

             No failure to exercise, and no delay in exercising, on the part of
the Secured Party, any right, power or privilege hereunder shall operate as a
waiver thereof; nor shall any single or partial exercise of any right, power or
privilege hereunder preclude any further exercise thereof or the exercise of any
other right, power or privilege. The remedies herein provided are cumulative and
not exclusive of any remedies provided under the Loan Agreement, the Note, and
the Other Documents or by Law. Debtor waives any right to require the Secured
Party to proceed against any other person or to exhaust any of the Pledged
Collateral or other security for the Secured Obligations or to pursue any remedy
in the Secured Party's power.

         10.  Assignment.
              ---------- 

             All rights of the Secured Party under this Agreement shall inure to
the benefit of its successors and assigns.  All obligations of Debtor shall bind
its successors and assigns; provided, however, Debtor may not assign or transfer
                            --------  -------                                   
any of its rights and obligations hereunder or any interest herein.

         11.  Severability.
              ------------ 
             Any provision of this Agreement which shall be held invalid or
unenforceable shall be ineffective without invalidating the remaining provisions
hereof.

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         12.  Governing Law and Jurisdiction.
              ------------------------------ 

             This Agreement shall be construed in accordance with and governed
by the internal laws of the State of Delaware without regard to its conflicts of
law principles, except to the extent the validity or perfection of the security
interests or the remedies hereunder in respect of any Pledged Collateral are
governed by the law of a jurisdiction other than the State of Delaware. The
Debtor hereby irrevocably consents to the exclusive jurisdiction of the courts
of the Commonwealth of Pennsylvania located within Philadelphia County or the
United States District Court for the Eastern District of Pennsylvania for the
resolution of all claims, disputes and controversies arising hereunder.

         13.  Notices.
              ------- 

             Debtor agrees that all notices, statements, requests, demands and
other communications under this Agreement shall be given to each of the parties
at the address set forth below their names and the manner provided in Section 7
of the Loan Agreement.

         14.  Specific Performance.
              -------------------- 

             Debtor acknowledges and agrees that, in addition to the other
rights of the Secured Party hereunder and under the other Loan Documents,
because the Secured Party's remedies at law for failure of Debtor to comply with
the provisions hereof relating to the Secured Party's rights (i) to inspect the
books and records related to the Pledged Collateral, (ii) to receive the various
notifications Debtor is required to deliver hereunder, (iii) to obtain copies of
agreements and documents as provided herein with respect to the Pledged
Collateral, (iv) to enforce the provisions hereof pursuant to which Debtor has
appointed the Secured Party its attorney-in-fact, and (v) to enforce the Secured
Party's remedies hereunder, would be inadequate and that any such failure would
not be adequately compensable in damages, Debtor agrees that each such provision
hereof may be specifically enforced.

         15.  Dividends; Voting Rights in Respect of the Pledged Collateral.
              ------------------------------------------------------------- 

             So long as no Event of Default shall occur and be continuing under
the Loan Agreement, Debtor may exercise any and all voting and other consensual
rights pertaining to the Pledged Collateral or any part thereof for any purpose
not inconsistent with the terms of this Agreement, the Loan Agreement, the Notes
or Other Documents; provided, however, that Debtor will not exercise or will
                    --------  -------
refrain from exercising any such right, as the case may be, if such action would
be inconsistent with the covenants and obligations of Debtor under the Loan
Agreement and the Other Documents or would have a material adverse effect on the
value of any Pledged Collateral. So long as no Event of Default has occurred and
is continuing, any lawful dividends paid in cash to Debtor in respect of the
Pledged Collateral may be used or applied by Debtor for any purpose permitted by
the Loan Agreement.

         16.  Entire Agreement; Amendments.
              ---------------------------- 

             This Agreement constitutes the entire agreement between the parties
with respect to the subject matter hereof and supersedes all prior agreements
relating to a grant of a 

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security interest in the Pledged Collateral by Debtor. This Agreement may not be
amended or supplemented except by a writing signed by the Secured Party and
Debtor.


         17.  Counterparts.
              ------------ 

             This Agreement may be executed in any number of counterparts, and
by different parties hereto in separate counterparts, each of which when so
executed shall be deemed an original and all of which taken together shall
constitute but one and the same agreement.

         18.  Descriptive Headings.
              -------------------- 
             The descriptive headings which are used in this Agreement are for
the convenience of the parties only and shall not affect the meaning of any
provision of this Agreement.

         IN WITNESS WHEREOF, the parties hereto have caused this Agreement to
be duly executed as of the date first above written.


                             SECURED PARTY:

                             VDC CORPORATION LTD.

                                   BY:  /s/ Graham Ferguson Lacey
                                        -------------------------
                                   Graham Ferguson Lacey, President

                             DEBTOR:

                             PORTACOM WIRELESS, INC.

                                   BY:  /s/ Douglas C. MacLellan
                                        ------------------------
                                   Douglas C. MacLellan,
                                   President and Chief Executive Officer



[SEAL]
                             Principal Place of Business:

                             10061 Talbert Avenue - Suite 200
                             Fountain Valley, CA  92708

                             Chief Executive Office:

                             10061 Talbert Avenue - Suite 200
                             Fountain Valley, CA  92708

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                                   SCHEDULE A
                                        
                                       TO

                                PLEDGE AGREEMENT

                       Description of Pledged Collateral
                       ---------------------------------


                                                   Type and
Debtor                                        Amount of Ownership
------                                        -------------------

PORTACOM WIRELESS, INC.             4,000,000 Warrants to Purchase Common
                                    Stock of Metromedia Asia Corporation

                                      -9-