I'm having some troubles saving PDF files. I'm using Acrobat Reader DC Version 17.009.20044.25828 on Windows 10. The issue is the same on several PCs, some with Windows 10 Creator Update and come without.
The issue is totally random, is not connected to a specific file or folder.
Randomically when I open a PDF file, either from Outlook, from a remote shared folder or even from a local folder, when I try to "Save as..." I receive the message "The file may be read-only or another user may have it open. Save the document with a different name or in another folder" (roughtly translated in english from the message in my native language, italian).
Obviously changing name or folder doesn't solve the issue.
This problem is maddening, sometimes I close the file, open it again and it works, sometimes there is no way to save the file.
Checking on some forums I've found a couple of possible solutions, such as set the PDF/A mode as Never or disabling the preview panel in Explorer. None of these worked.