Why? You can do it in any drafting program, even Gimp or Photoshop. It takes less time on the computer. Not much different if you use a drafting program. All the computer is doing is the math from your measurements, and computers are good at that. You are still using graph paper but it's digital. You don't buy the software to not use it. Gimp and Inkscape are open source programs and free. Whole tutorial on Gimp somewhere on this site.
The pattern instructions sizing was wrong. I cut out the printed template and stuck it on a ruler for a jig. Able to correct the original error. I used EQ7 since it was on the computer I was using. If I was using the Linux box, I would have used Inkscape which would be the electronic graph paper. I'd have the measurements printed out. In this case, I just might enter the size of the triangle and go in reverse. Put the QST back as a square and see what the actual size of the square you were supposed to use, was.