When you have completed drawing your design, roll, DO NOT FOLD, the vellum sketches, and take them to your local neighborhood printer. For relatively little money he should be able to convert your drawings into beautiful blueprints. I was surprised at how easy and inexpensive it is to make blueprints. You can make an official looking blueprint out of dang near anything. Take a drawing of your favorite subject, a photo of a WWII bomber with a painting of some fetching blonde on its side for example, trace it onto vellum, and have it blueprinted. It comes out great!
I'm thinking about having our dining room wall papered with the stuff as my next home improvement project
The truly remarkable thing about blueprints is the psychological effect they have. They look authoritative. Like a dictionary, they carry the weight of moral certitude. For this reason, you should be careful to include in these drawings your desire or perspective regarding any possible future dispute between your wife and yourself. If she questions the mirrors on the ceiling in the bedroom or the built-in gun rack in the bathroom, just lead her by the nose to the blueprint and show her..."It's in the plan." How can she argue with that?
When the blueprints come back from the printer, you will be ready for the most painful part of the addition building process...getting the permits.