Error when opening a PDF file with Acrobat Reader

Hi,
I was opening a PDF file when this error message popped to my screen, see below. It was an attachment from the email and tried downloading it again. It was a very important document and I had no means to contact the sender for him to resend the attachment. Is there a workaround so I can open the file properly?

Acrobat could not open ‘Reply Envelope.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.)
To create an Adobe PDF document, go to the source application.
Then print the document to Adobe PDF.
