This is the page (and the 'Supported Printers' link there) [1] to goto to find out if a HP printer is supported by the free software hplip driver. You might need a version more current than in Trisquel 6.0 if your printer is more recent. There are a couple of methods to get the latest version on that page.
[1] http://hplipopensource.com/hplip-web/downloads.html
