Different/Secure Passwords in a Plug-in

I am developing fillable PDFs for my company to send to survey participants, however I have hit a bit of a road block in providing all the serivices we need.  I need to be able to encrypt multiple documents with different passwords at the highest encryption setting. (AES - 256).  My understanding is that I cannot do this without either writing a plugin or using LiveCycle.

If someone could help me witht he following questions:

1. Can I program the plugin using VB.NET or does the plugin have to be C++
2. Can this be run from a separate executable, or will only  plugin work?
3. Is there a good reference outside of the SDK documentation for programming this?

Any help is appreciated

Jim