There are online file converters and browser extensions that convert web pages into full PDFs, but for a simple, no-software-required solution, PDFmyURL spits out PDF files when you plug in a web address. And, yeah, there's a bookmarklet.
If you just want a PDF of a given URL at a certain time, PDFmyURL gets the job done with no fuss, no muss. You can also grab the bookmarklet from the front page to pull off the conversion at any time.
Click the "Advanced Options" on the right, though, and you'll learn how to pull off PDF production without even visiting the site, embed advanced options, and even run PDFmyURL from your own server. Neat, free stuff, and a great public service.