This sample demonstrates how to encrypt the PDF document with encryption standards like 40-bit RC4, 128-bit RC4, 128-bit AES, 256-bit AES, and advanced encryption standard 256-bit AES Revision 6 (PDF 2.0) to protect documents against unauthorized access.
It is possible to protect with user password or owner password or both passwords and also possible to change or remove password and permission. More information about encryption or decryption can be found in this documentation section.