Also check out this website for a lot of other useful HP cartridge tricks, like getting the printer to accept refilled cartridges and more: http://inkjet411.com/
Even if it says "View" on the site, clicking a link to a printer opens a .pdf file that you can save.
Edit: The link above doesn't work any more, but the company still offers service manuals for very many HP laser printers. They are no longer free but are sold at 1$ per download. The new address is: https://www.feedroller.com/service-manuals.html