There was an error opening this document. Can't decrypt this document.

[TUGOI]

I opened a PDF file in Adobe Acrobat 8.1 but this message popped up. The PDF file has no password. This is the first time I'm opening the PDF file using Acrobat 8.1.

[Test Screen Name]

That's very old. Can you open it in current Acrobat?

By the way, one cause of this is disk corruption, and another is ransonware attack.

[Test Screen Name]

Oh, but careful. Installing Acrobat DC will uninstall Acrobat 8, and you will NEVER BE ABLE TO GET IT BACK.