The answer to this depends on the printer you're using and how your job was submitted. The various options are described below.
If you submitted your print job to the Pharos old-and-release printing system, the answer is simple: You cannot cancel your print job. Instead, just don't release the print jobs you don't want. Any unreleased jobs will be pruned from the queue after 4 hours.
If you have already released a print job and you don't want it, you can press the red stop button on the printer, and use the up and down arrow keys to navigate to the menu option Cancel Job. Press the green checkmark button to select the option. The printer will print the remaining pages cached in its memory, and then stop.
Note that your print quota will be debited
For private or DLC printers with an Athena print queue, you may be able to cancel them with the "lprm" command.
To remove all your jobs in a particular printer queue, type:
To remove a single job from the queue, type:
...where '#' is the number of your print job (obtained from the output of the lpq command.
Use the printer's "cancel job" feature to cancel the job. Consult your printer documentation for the correct method of canceling the job.