Printer problem

[Barry]

Having cancelled a print job, how do I empty the print buffer to save 
time ink paper and frustration without closing down & rebooting????

Cancelling the job in CUPSdoesnt work. Switching off the printer only 
appears to empty the printers internal buffer, is the print queue held 
in memory, or on file somewhere?

I know others have had this problem, what is the answer please

TIA
Barry