I've evaluated already some number of PHP libraries and html2pdf seems to be have the highest quality. But even it has some issues:
It looks like html2pdf does not support subj. by that I mean css attribute liek font-size:x-small. But it is from CSS standard and we use tinyMCE to edit some of HTML part and tinyMCE uses that named font-sizes.
Do you plan to add this feature?
Nonetheless it looks like I'll make a change for html2pdf. Where should I send my patch if it will be ready?

BTW didn't you thought that comments in English would make library much easier to use (the same goes about the site/forum)?

And thanks for a good library