Sorry for the inconvenience caused to you. Kindly share with us your machine details and Acrobat version.
Also are you facing this issue with a particular document or this is a generic issue.
An error occurred while saving the commentAnonymous commented
We need a way to save all open PDFs in Acrobat DC at one time to close out PCs without having to try and save each individual PDF already open in the Acrobat DC Program and we need Acrobat DC to automatically save whatever is open in Acrobat DC program in case of a crash when we restart our computers.