It's called US mail. If you want it faster, there's something else called courier service. I believe he used the latter.
He did receive a hard copy, BTW, (I believe it was two, actualy), and they were shown to reporters. Someone at the Whitehouse then scanned one of these hard copies to create a pdf in order to post it online.
For some reason, the fact that it's impossible to post a physical document on the internet seems lost on most birthers.