Hope you are doing well and sorry for the trouble. As described you are unable to open the PDF file and getting the error 'file is corrupted and cannot be repaired'
Acrobat pdf files are sometimes treated as if they are ascii files rather than binary files. This causes them to be corrupted as since mail handlers will sometimes handle ascii attachments differently than binary attachments. The work around is to zip or otherwise compress the file so that the attachment will be treated as a binary file.