When saving as PDF, you can add password protection and security restrictions, limiting not only who can open the file, but also who can copy or extract contents, print the document, and more.

A PDF file can require passwords to open a document (document open password) and to change security settings (permissions password). If you set any security restrictions in your file, you should set both passwords; otherwise, anyone who opens the file could remove the restrictions. If a file is opened with a permissions password, the security restrictions are temporarily disabled.

The RC4 method of security from RSA Corporation is used to password-protect PDF files. Depending on the Compatibility setting (in the General category), the encryption level will be high or low.