There’s several tools in Ubuntu to convert from PS, DVI, TeX, et. al. to PDF. There’s also several tools to convert from PDF to PS, ASCII, HTML et. al.

But if you want to convert from HTML to PDF (and keep stuff like hyperlinks, for example), printing to PDF from Firefox won’t do the trick, you’ll need htmldoc.

Otherwise, there’s also services like http://www.htm2pdf.co.uk/