Perfect PDF Security is a safe and user-friendly application for protecting your PDF documents using AES and RC4 encryption algorithms. It supports all standard key length and versions of PDF security.
The multiview (multiple files in own windows) possibility is on board now!
Features:
Encryption / decryption of PDF documents, modify PDF security properties and user permissions
Quickly open PDF & XPS files
Various viewer layouts, fit modes, zoom tools and search in document text available
Print documents with different layout options
Navigate using links, outlines and/or semantic zoom
It worked really well when I used the password protection to open the document. It would be good to have some better instructions on what the encryption and the other protections mean.