Have a document that was received via 3rd party by a user. It had a digital signature, that was invalidated prior to receipt. However, when the user opens the file, he doesn't see the invalidated digital signature. He has since edited the invalidated PDF and receives errors when he tries to save the file with his changes.
Furthermore, the document properties after his changes are updated to Not Allow changes. But, he can re-open the document the make additional changes, and resave the PDF with error messages and those changes are saved as well.
That user is using Acrobat 11 Pro. When I open the file, I can see his changes, the invalidated signature, and if I choose to edit the PDF using Acrobat DC Pro, receive the error the PDF is secure and no changes are allowed.
Any thoughts, why Acrobat 11 allows the edits and doesn't show the invalidated signature?