To cancel a print job in the queue just use cancel. To see all the available jobs in the queue just use lpstat.
$ lpstat -o HP-Officejet-7610-2-128 user2 240640 mié 09 mar 2016 11:07:14 CET HP-Officejet-Pro-8620-137 jose 55296 dom 03 jul 2016 13:29:49 CEST $ cancel -a HP-Officejet-7610-2-128 $ cancel -a HP-Officejet-Pro-8620-137