...is as follows:-
To re-enable access to blocked Web links that are contained in the ?envelope? for a protected PDF document, follow these steps:
1. Start Adobe Acrobat or Adobe Reader.
2. Open the Preferences dialog by selecting the Edit > Preferences.
3. Select the Trust Manager panel on the left side of the dialog.
4. Click the Change Site Settings button at the bottom of the dialog. You will see the Managed Sites dialog. This dialog contains the Trust List.
5. One by one, highlight the entries for each adobe.com web site that appears in the Trust List, and click the Remove button.
6. Click OK to close the Managed Sites dialog. Then click OK to close the Preferences dialog.
You can use the same process to re-enable access to any link embedded in a PDF file.
I hope it's of use to some of you!