I recently switched from EagleCAD to KiCAD, and so far I'm very happy
with it. It took a few days to get my head around it, but I think
that's fairly typical of CAD software. It will generate PDFs of your
schematics, which is probably the most appropriate distribution file
format.
http://www.kicad-pcb.org
I recommend you put an explicit copyleft license on your schematic,
e.g cc-by-sa:
http://creativecommons.org/licenses/by-sa/3.0/