I trace them with the pen tool in Photoshop, then I flatten the layers (as a copy, in case I have to go back and make changes) and break them into tiles, save the tiles as grayscale JPEGS, and place them into an InDesign document. I make the PDF from InDesign using the PDFX1a preset. This results in a file that is usually around 3-5 Megs depending on how many pages are in the pattern.
There is a free program called the Gimp that is supposed to work like Photoshop, but I've never tried it. I'm a graphic designer, so I have to have all the Adobe software anyway.