Docotic.Pdf library can open and create documents encrypted with standard encryption algorithms.
You can remove encryption from your PDF documents. And, of course, you can protect produced PDF files using RC4 40-bit, RC4 128-bit, AES 128-bit, and AES 256-bit encryption algorithms.
You can setup what permissions you want to grant to users of your PDF files.
All permissions defined by the latest PDF standard are supported.
Take a look at a short sample that shows how to set up user access permissions for a PDF document.