You can use WPS Office to make your PDF restricted with edit restrictions. If the user applied password for this, then no one is able to edit your file. If the user have files in bulk then you need a trusted automated tool. In this scenario the technical experts of SysTools give their Best PDF Lock Tool.

Steps to use this method.
Step 1. Download the software to your computer.
Step 2. Add files to make them secured.
Step 3. Click Next and select encryption after entering password.
Step 3. Click the Lock Button from your window.