Encrypting PDF files with owner and user password is an ideal way to protect your authority and copyright. A user password can help you to control the permission of opening a PDF, while the Owner password can protect your PDF files from reuse. Obviously, Adobe Acrobat Pro is too expensive to personal use, so Vibosoft comes here to take your thought into considerations and release this PDF Locker to help you protect your PDF files completely. Strongly Lock PDF Files with Own Password and User Password. Three kinds of encrypt algorithm: 128 bits AES, 128 bit RC4, 40 bit RC4. Set a variety of privileges to permit printing, copying, editing or modifying. High Stability: Load hundreds of PDF files at a time and doesn't crash.