Appnimi PDF Password Kit is a handy tool to lock or unlock any zip file with a password. It can be done in 3 easy steps: Steps to Unlock a protected PDF file: 1. Select the PDF File 2. Enter the password of the PDF file 3. Click on the Unlock button on the right. Steps to Lock an unprotected PDF file: 1. Select the PDF File 2. Enter the password you want to use to protect the PDF file 3. Click on the Lock button on the right.