unable to open pdf

[AtkinElw]

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.

Thanks

 

[jaspercasper07]

Hi, does this only happen for a specific set of PDFs or all of them, regardless of source?
In any case, the said files might be getting corrupted by malware trying to infect the documents, eventually failing to infect them correctly. If it is the case I'll redirect your post to the Viruses/Security subforum in the hope someone will help you clean the computer.
http://www.reddit.com/r/pdf/comments/2d52rm/how_to_fix_format_error_not_a_pdf_or_corrupted/
Can you also try to open the files with different PDF reader, e.g. Firefox if it is installed (it can read PDFs directly thanks to
pdf.js)?