I've just tried out HTML::HTMLDoc and (the current version) doesn't support much in the way of CSS.

The problem is, of course, that in order to format a web page correctly for conversion to PDF, you have to build what amounts to a web browser. So my thoughts were, well, why not use Firefox to do that?

You'd think that would be easy, surely just a command line option that would use the existing code to print to a PDF, rather than launching a browser window. Naturally, I'm not the first person to think of that. However, this feature request, which is not the first, was opened in 2001, and seems to be well and truly stalled.

In that bug, they do mention gnome-web-photo, which I realise won't be of much use to you, as it is for Linux, but I tried it out, and it works rather well. It is available as a package on openSuSE at least, I presume on other Linux distributions as well.

It produces PS files, which are easy to convert to PDF docs with ps2pdf.