You don’t have to use the included editor or the server in order to generate the pdf.
You can setup a local workflow with a local LaTeX environment and configuration.
I will not got into detail how to setup a local environment. There are tons of tutorials already available.
Once everything is setup, the process is straight forward.
*nix example:
Step 1: gtx -> tex
# java -jar GuitarTeX2Convert.jar -f file.gtx > file.tex
Step 2: tex -> pdf
# pdflatex file.tex