It is truly doubtful that the update had anything to do with the problem. The problem most likely has something to do with the file. It is possibly corrupt. However, there are many 3rd party utilities that can remove password protection from any pdf file. If the file is not corrupt the information can be easily retrieved.
This is fine if only it was one file. But every file that has a password is the same. Ones that could be opened the day before the update but not after.
So if it is true the file got corrupted, HOW when the only thing done is an update from 5 to 9.0? Plus the files in question are bank statement files covering two years. I also copied one from a backup onto the system same result. ? At present I am running a password retrieval software on one copy of the file to see what it comes up with. But the password on these PDF's has not changed in approx 3 years.
Another issue to mention. I uninstalled threw MS rebooted, tried to install an older version(7 was as far back as I could go) it stated that is installed fine. But the same issue. But this time No PDF files on the system include the Adobe Icon. When clicking on one it brings up the version 7 now, but with the same results. But now every time it give me an explorer error too. Saying it quit running.