You don't need the GuitarPro software, you need GuitarPro-format files.
GuitarPro is a pretty common format for machine-readable sheet music. Most "tab editor" programs can open and save to the GuitarPro file format. TuxGuitar is one example of a tab editor that is both good and free and does this well.
But you don't need to do that either. There are tens of thousands of GuitarPro format files readily available on the Internet. Ultimate-Guitar is one major source but there are lots of others.
EDIT: Name a band or a song and I'll import one for you. (Just don't go out of your way to "stump" me with an obscure choice).
