Marcus Bointon has written up the process he took to get the PHP extension for Wkhtmltopdf (a conversion tool for HTML to PDF generation) up and working on a Mac OSX machine - not as easy a task as it sounds.
Wkhtmltopdf is extremely cool. I've used qtwebkit for generating server-side page images before using python-webkit2png, and that's fine (unlike using Firefox running in xvfb!), but I need to produce PDFs. So, I looked around and found several neat, simple PHP wrappers for calling wkhtmltopdf, and even a PHP extension. "Great", I thought, "I'll just install that and spend time working on the layouts since the code looks really simple". I spoke too soon.
He goes through each step of the process - installing the needed wkhtmltox and libwkhtmltox support, having to manually compile wkhtmltopdf and some of the small changes you'll need to make to the Makefile to get things to cooperate. He shows where to put the resulting application files and the name of the extension to enable in your php.ini.