Thanks for getting this done. But come on, CURL is documented pretty well. There are even examples. What's there to know? Init a connection, set the flags, pass in whatever you like, submit, and check response. Pretty straightforward to me.
The CURL stuff seems so oddly unlike the rest of the PHP commands; it's more-or-less a direct port of the c++ library, names & all included.
The place where it reallllly irritates is the cookie management, but thankfully I didn't have to deal with that in this case. (I did for a client at a newspaper - nightmarish.)
Try it:
http://www.tokyomuslim.com/2010/04/php-class-to-run-pdfcrowd...
I don't blame anyone for not wanting to use PHP's poorly documented CURL classes.