In the continuation of bug/enhancement request 1276 (suggest declaring
PDF's members protected -
http://dev.processing.org/bugs/show_bug.cgi?id=1276), I will suggest to add
an OutputBuffer field (see Write PDF to Byte[] (without writing a file!) -
http://processing.org/discourse/yabb2/YaBB.pl?board=LibraryProblems;action=display;num=1237962559
thread for motivation).
The idea is that the OutputBuffer will be created in the setPath() call,
instead of in the beginDraw() call, as it is done currently. Thus, we can
set the output buffer ourself before calling beginDraw which would use
whatever output we need.
I haven't looked but I suppose this applies to the DXF exporter as well.

I think it is a minor change, not altering compatibility, opening the lib
to advanced users (or other libs like the SaveToWeb one) without the need
for awful hacks... :-)

Sure, I'll look into it. This had occurred to me when creating the library,
so I think there was a reason that I didn't do this in the first place
(writing to a buffer in general), but I'll take another look for you.

k, adding this to PDF for the next release. the idea is to use:

PGraphicsPDF pdf = (PGraphicsPDF) createGraphics(w, h, PDF);
pdf.setOutput(yourOutputStream);

then i've added bug #1502 to look at the larger setOutput() issue.