Yesterday I succeeded in getting my RaspberryPi2B to print on a USB printer (HP LaserJet Pro 400). I then attempted to print results from the Pi version of Mathematica 10. I soon found there is no Print menu in the version I have installed (10.0 for Linux ARM (32 bit) (Feb 3,2015)). However, as a work-around - I found you can Save As (then select PDF) and then print the PDF file that corresponds to the entire notebook with the Pi's PDF Viewer application. Mathematica's Export routine allows finer grained saving of results to PDF.