Acrobat could not open attachment.

Hi guys,
My attachments in blogs get damaged. The error message given below, I get when trying to open or download an attachment.
Can anyone suggest me about this issue?
Thanks for help.
Acrobat could not open 'moodle_usually_study_quiz_tool.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.
