Almost all of it wouldn't be useful in a PDF document. What exactly were you thinking about using it for?
One thing you could uses Jquery for, would be to work with SPservices so you could easily connect to SharePoint list information and pull it into your form. I have not found an easy way to do this yet.
To access the OS or web services one needs to write a plug-in or use the Soap object. You might want to download and study the Acrobat SDK.