The SDK is primarily concerned with COS level access. You want some higher level functions for form field Handling. These functions are located in the "Forms API", which is an HFT in the SDK. You can include it when you run the plug-in wizard for a new project. The documentation should be in your Acrobat SDK documentation.
Thom Parker
The source for PDF Scripting Info
www.pdfscripting.com
Very Important - How to Debug Your Script