Yes, it is very available. It's called a CAM (Computer Aided Manufacturing) program. Look at Fusion 360 by AutoDesk, full professional CAD/CAM package, free to hobbyists, startups, and educators/students, inexpensive for established shops. Another very simple option is CamBam. Either of these programs will allow editing a DXF file, but the CamBam drawing editor is a bit clunky.
You really want to bring the DXF into a drafting (CAD) program, then process with the CAM program to generate the G code.
EDIT: What is it that you are needing to move around in G code? Are you actually modifying the engineered hole locations?