Adobe Reader / Acrobat documents with a *.pdf extension are the most popular document format at the moment. A PDF file, like any other file, may get damaged, and you may see various error messages when trying to open an Adobe Acrobat / Adobe Reader file. As the result, the document ends up being unreadable
One of the main reasons why these issues occur is the incorrect operation of different software: browsers, email clients, the operating system, anti-virus tools, firewalls and such.

The simplest ways of solving this problem are:

download the document again
restore a backup copy of the file
recover the previous version of the document
Unfortunately, if you cannot recover the document using these methods, Adobe does not provide clear guidelines regarding the recovery of PDF files. If you go to the official forums at https://forums.adobe.com/, you won’t find a direct answer; but some users suggest the following ways of recovering PDF files
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