I have a password-protected PDF that I opened, filled in forms and signed. I then saved and exited. When I try to reopen it, the password is not recognised. Using Reader on a MacBook Pro. I've also gone back to the original PDF (email attachment) and open it with Mac Preview. Same issue.
Do NOT open the file in Preview, at any point. It's a faulty application, known to corrupt PDF files. Go back to the original and only open it in Reader.
Thanks, that worked. I don't agree with your opinion on Preview. It's a great app for an everyday user like myself. This was the first time I think I've had an issue like this.