I have an end user that is running into a periodic issue where when she attempts to save a file that has been digital signed, Reader will become unresponsive and close. However, it doesn't happen all the time. For example, I was standing next to her and when she signed something, it saved just fine.
Anything I can do to help her?
Sorry for the delay in response.
Check if you have any pending updates, to check, launch Acrobat > Help > Check for updates. Also, try repairing the application to repair Acrobat/Reader > Help > Repair installation (Applicable to windows users only)
Also, you may try launching Reader with Admin rights.
If you already have found a solution to this problem, please update the thread with your findings that will help others.