Comment 4 for bug 521533

I just noticed the same issue. I had stored some filled out forms on an encrypted drive. I ran into a bug where the fields I entered didn't weren't being displayed after being saved (not even an empty field). I figured the file had been corrupted so I copied the original blank form over the filled out one. When I opened it all the information I had entered into the form was there despite the file having been overwritten. After looking around I found it had been written to .kde/share/apps/okular/docdata - on an unencrypted drive. This was quite startling to me and not what I expected.

I can understand if there are limitations to the PDF format that prevent you from storing the data in the PDF file itself, however you should at least inform the user of where the data is being stored before writing it. Preferably, it should be stored in the same directory as the PDF as well.