Is it possible to save pdf files as read only so that no one else can unlock the files?

Hi @default6ladyexzwiyz 

++ Adding to the suggestion by try67

Please go through the help page https://helpx.adobe.com/acrobat/using/securing-pdfs-certificates.html for more information and know-how.

Regards

Amal

The best way to do that is to digitally sign the file, and also to apply a security policy for it that prevents editing AND requires entering a password to open it.