I printed the wrong file

Use the cancel jobID or lprm jobID command.

My print hasn't come out

Use the lpstat or lpq command and see if you can spot your jobID (see man lpq or man lpstat to find out more).

If your jobID is not there, contact your system administrator. If it is, check that the printer is currently printing. If so, just wait, your job will get done in due time.

If the printer is not printing, check that it has paper, check the fysical connections to both electricity and data network. If that's OK, the printer may need restarting. Ask your sysadmin for advice.