How to edit a PDF created with Acrobat XI Pro after signatures have been applied (like I can in 7, 8.0

Question

I have a major issue that I need to resolve before we can purchase Acrobat XI Pro:
Currently, with Acrobat 8.1 Pro, after all signatories sign a document, we add an Effective Date (we add it after they sign since we don't know when the last signature will be acquired and we can't have an Effective Date that is before the date of the last signatory, otherwise, it would be effective before they signed it, which is not possible). I'm also allowed the latitude (as stated in our Documentation Control procedure) to make spelling corrections, hyperlink updates and minor formatting changes (by using the typewriter tool and also by replacing a page that is NOT the signed page if the change repaginates the document or involves modifying a hyperlink that has changed).
In all of the previous versions of Acrobat that we've used (7 Pro, 8 Pro and 8.1 Pro) , this has been easily possible and all changes would be listed under the Signatures tab, which is exactly what we want, which is traceability.
I'm using the trial version of Acrobat XI Pro now but am getting the message "This document is signed and can not be edited." If I bring the same PDF that was created from Word 2003 & 2013 using Acrobat XI Pro into 8.1 Pro, though, I CAN add the date, use the typewriter tool and replace non-signed pages, save it and exit without clearing or losing any signatures.
My question is this: How can I do this in Acrobat XI Pro, as XI Pro (in the Signature pane) also lists the changes made to the document when it was edited using 8.1 Pro? (It's OK that the changes made to the PDF then mark the signatures as "invalid", as the reason why they were invalidated is also listed in the Signature pane, e.g. "Form Field Added", which is usually the applied Effective Date.)
Thanks for any help!

Answer 1

Acrobat versions prior to 9 had a bug which allowed you to do what you did. In Acrobat 9 this bug was fixed. In order to do what you want you need to certify (apply special certification digital signature with your certificate -- it is "Certify (Visible/Invisible)" choice in the "Work with Certificates") your document first. In the process of certification you can specify which modification permissions you allow the users of your document to make after signing. Certification signature must be the first signature in the document.