Can you please provide the following details :
1. Does the app freezes when you try Fill and Sign with all PDF files or specific PDF files. If possible can you please share a sample PDF.
2. Did you try using Comments/Edit after opening the PDF?
3. Once the application freezes, open task manager and go to Acrobat.exe process, right click and create a process dump. Kindly share that with us.
An error occurred while saving the commentMatthew Weeks commented
I had a similar thing happen; the fill and sign would freeze when I tried to add initials (it already had my signature saved). I was able to fix by killing the process, deleting all appdata Adobe folders and HKCU\software\adobe and restarting.