One thing to check is at an OS level, when you click on that type of file, what application opens the file up, and is it the same as what you are expecting - this goes back to the OS level - what default application.
We had moved to an open-source PDf reader for performance and security reasons, but had to go back because AC didn't respect the OS level default program.
So, it is a mixed bag at best, especially if you go off the M$ reservation.
