My customer has recently encountered a problem when trying to open most of their pdfs that they have been referencing for years on their pc. Reader has a popup box that says "Adobe Reader could not open 'file.pdf' because it is either not a supported file type or because the file has been damaged (for example, it was sent as an email attachment and wasn't correctly decoded
I have tried various programs to recover/restore/repair them, they all say the files aren't PDF files. I have not paid for any recovery programs but would be willing to if they can demonstrate they can fix the problem first.