I use Adobe Acrobat 8 Professional (current version is Adobe Acrobat X). It has a menu option
File... Create PDF... From Web Page... which asks me for a URL, then it downloads the page at the URL as a PDF file, with searchable text. It will also convert pages linked to from that page, recursively. You can end up with many HTML pages in one multi-page PDF file, with inter-page links preserved.
For some web pages, Acrobat Create PDF gets the formatting wrong. In that case I fall back to the
Adobe PDF 8.0 printer driver which Acrobat 8 Professional installed on my system. It is very good at giving me a PDF equivalent of the web page I'm looking at, with searchable text.
Adobe Acrobat 8 Professional is not free software. It's fully-priced proprietary software. However IMHO it deserves as much a place in every knowledge worker's computer as does Microsoft Office. And, you didn't specify that you insisted on a free software way to convert a Web page into searchable PDF.