I have done some large format renders of factory floors. There are services in most large communities. You might want to check your local drafting or engineering supply store to make sure that they are already offering the service cheaper. At 1200 DPI for a C-size drawing the price can go for $15-$125 and they will want the file on a zip disk or CD-ROM. If you render and post process the file, you can request a binary print which some places will do cheaper because it takes less time. But, you have to print it for a specific printer to file. Each time that I have done it, I had to teach the service how to do it. I always get a free print for teaching them.