First of all, as there is no one-to-one correspondence between HTML and PDF, and the approaches in these formats are different, on input, you need not just some HTML, but also some mapping rules of your choice.
Ideally, HTML should be a well-formed XML, then you could use any of the XML parsers available in FCL. If you cannot assume well-formed XML, this is much worse: you would need some HTML parser which could cope with that. I would advise, for example, this one:
http://www.majestic12.co.uk/projects/html_parser.php[
^].
To produce PDF, you can really use the .NET port of iText; this port is called iTextSharp:
http://en.wikipedia.org/wiki/IText[
^],
http://itextpdf.com/[
^],
http://sourceforge.net/projects/itextsharp/[
^].
I provided links to iText, too, because nearly all documentation you need to work with iTextSharp is there, provided as Java documentation.
—SA