PDFEncrypt is a free, open-source Windows application that encrypts any PDF file using industry-standard encryption algorithms.
Free • Open Source
What is PDFEncrypt?
PDFEncrypt is a free, open-source utility for Windows that encrypts any PDF file using industry-standard encryption algorithms. Simply select the unencrypted file, enter a password, and the encrypted file is generated. PDFEncrypt also provides advanced settings and features like "run program after encryption is complete" so that it can be used in a toolchain of other apps.
I cannot believe how I survived without this software. I often need to print documents from public computers. This software is lightweight and does the work perfectly. It supports 32 characters for password.