There is an "identity" object that can be accessed by AcroForms and LiveCycle Designer but you will have to deal with some security issues depending upon the version of Acrobat/Reader a user is using.
Did you find a solution regarding your question? I also would like to pull user's information from AD like Full Name and title then put it in a dynamic stamp.
As Patrick says, for security reasons there is absolutely NO access to the user's personal information beyond the properties exposed in the identity object, and that is only visible to folder-level scripts so nothing inside the document itself can read them.
The only way to get the data into a PDF would be to write your own SOAP service, which of course would only work inside your own Windows network. That's a problem beyond the scope of these forums.