Open the printer queue from the printer icon in the system tray or from Printers & Scanners
Select the printer
Open the print queue
Cancel all pending documents
If documents do not clear, stop the Print Spooler service
Delete the files in the spool folder
Restart the Print Spooler service
Restart the printer and computer if needed
On Mac, open Printers & Scanners, select the printer, and clear the queue
On Windows, use Services to restart Print Spooler if the queue is stuck