When you save a PDF in Acrobat DC on Windows 10, you get an error: "The file may be read-only, or another program may have it open. Please save the document with a different name or in a different folder."
Controlled folder access is a Windows 10 feature that helps protect your documents and files from modification by suspicious applications. The above-mentioned error appears when Acrobat DC is denied permission to save PDF files on your computer. You have to add Acrobat to the list of safe or allowed applications in controlled access folder settings.