In case someone has already answered your other post, please ignore.
You could go hunting around in the registry for the user details, but
I don't know how much success you'd have in extracting the required
information. I had a bit of a play with that but with little success.
Two easier methods I can think of:
1) Use the "Application.UserName" property.
2) Prompt the user to provide their name via a dialog. (or perhaps get
UserName first, then display it to the reader and give them the chance
to edit it)
In either case, once you've got the above info, write it out to a file
or append it to your document.
All the best,