Hi. I am having the same issue but the strange thing is that some pdf files (using extension to download pdf files) download correctly and some don't. Have tested all pdf files locally before uploading and can open sucessfully (not the dowload function but double clicking on them). The same happens with files that are 2,5 MB or 32MB size. I mean it doesn't have to do with file size. Thank you.
PS. It's so strange. I can download correctly pdf files of 25MB and others of 2.5MB crash.
The error I am getting through Acrobat is "There was an error opening this document. The file is damaged and could not be repaired."