If you want to lock PDF files then you can do so using osttopstapp PDF Protector software. Users can lock multiple unlocked PDF files at once. After securing the PDF file with a password, it cannot be printed, copied, or edited by anyone without the owner's permission. You can set or reset the password of the PDF file. After securing PDF files - users can share them online also. No changes occur while locking the PDF file. You can store the secure PDF file at your chosen location. You can create the password of a PDF file by combining numbers, symbols, and alphabets. For the ease of users, they also offer a free demo pack to all which they know more about its functionality.