Well, pdf compilation dies partway through interlinking the indicies, leaving it quite difficult to navigate. I am not on Windows right now, so I did not try building a chm, but from my memory, chm only supports png (not svg), so it will be at least another 100 MB, unless diagrams are disabled (for reference, the site is 5 MB compressed, and the partial pdf is 17 MB). I suppose doxygen could be restricted to only read headers, to reduce total size (and potential for whatever is causing generation to fail), but then call reference and some other information will be lost.
If anyone wants to do further experimentation, my changes are attached. Run: doxygen sdk.doxy