Printing in Linux sometimes is a pain especially when you are a newbie. Simple things like killing a job might not work via the GUI. This is where the terminal comes handy.
Use the "lpq" command prior to using the "lprm" command to make it easier to see which print jobs are currently in the queue. The "lpq" command lists all of the files in the queue, as well as the user, the job number, the size and the root directories from which the print jobs originate.
Type the name of a specific user to remove all of that user's print jobs from the queue. For example, to remove all of the print jobs in the queue posted by the user "linux1" you would type "lprm linux1." If you want to stop just a job instead of username type the id of the job.
Use the "-p" command line parameter to remove print jobs from the queue of a particular printer. In this manner you also need to include the network name for the printer (by default, printers are labeled lp0, lp1, lp2 and so on). In order to remove all of the print jobs from printer lp2, for example, you would type "lprm -p lp2."