As a sidenote, if you download a file and it is not opening on Adobe Acrobat and PDF repair software does not work (or work well), there is a chance that the PDF file can be easily recovered with the preview application on a Mac.
If the PDF creates a thumbnail preview instead of the standard PDF icon, it should be able to be recovered. Simply open with the preview application and save as a PDF. Not sure exactly how the app irons out the corrupt parts but it works quite well.
So instead of throwing away a PDF you tried very hard to find and won’t open conventionally, see if it can be recovered on your Mac or email to a friend with a Mac.