I use Adobe Acrobat DC Pro to grade student tests. Students upload all pages as one pdf document in our LMS. I then, download, open in Adobe DC Pro, edit/grade, save, and attach graded tests for my online students to see their mistakes. I have always been able to "edit" their pdf upload and make corrections without a problem. This year I am requiring an instructions page to be included with a parent signature (whether hand written or typed) and that is the first page (of usually 3 in the pdf). Today when I opened a student's test, there was a pop up that asked me to automatically allow something (I can't recall exactly) with the signature, and I checked "yes" and "run automatically". The problem is now I can't edit/grade the test, since it recognized a signature, and I can't make changes. How do I change my settings to go back to what I had before?
You might try:
Edit > Preferences > General > Warnings > Reset All Warnings
Edit > Preferences > Signatures > Verification
which has a number of options related to digital signature validation.