I did a lot of commenting in a PDF-Document on Acrobat DC on iOS. While syncing it to the Document Cloud, there occured an error, obviously because the app was updating itself at the same time (needed to sign in again with my account). This resulted that the PDF-File crashed completely and wasn't able to open again ("document error"), even with the desktop version of Acrobat. So all the work lost. Not good! I liked the new DC features, but if this means Acrobat gets unreliable, I cant use it for professional work.