Be careful with what you wish for...
I wouldn't save any type of line drawing to jpg, it would be better to save as png, tif, or bmp. Because jpg does a type of averaging of colors for compression, the crisp, black lines will be averaged with additional grey points and will fuzz out. This averaging will cause the file size to become quite large. Jpg's should be used for photographic type images with a lot of colors and not much blank space. Universal Document Converter will create bmp, jpg, tif, gif, pcs, and dcx, but, may not be as crisp as you expect, but it works well. Photshop adds a grey line to the black and will not be crisp at magnification, but, it too works well.
The best (IMO) way is to get the free GSview (also known as Ghostgum) from the University of Wisconsin website at:
http://www.cs.wisc.edu/~ghost/gsview. Download and install both GSview and Ghostscript and install per instructions on the website.
You can then convert your pdf to a high resolution (you can choose 72, 300, or 600 dpi) png, or tiff. Png is better because of its smaller file size when dealing with images a few colors such as black & white or greyscale or "pure color" such as vector or clip art. Gif will produce the smallest file size but the quality may suffer.
The examples below are all derived from a 24" x 36" plot of a floor plan, saved as pdf in DataCAD 11, opened in GSview, and saved a png and a jpg. Irfanview was used to crop and copy. The final image composed in Lotus Freelance, saved as a bmp (1229kb), converted in Irfanview to a png (36kb) for posting. (The gif was made using Universal Document Converter.)
Note the file sizes gif = 91kb, pdf = 177kb, jpg = 3,112kb, and png = 351kb.
Iknow, I know...too much information, but, I hope it's helpful.