Shows you have poor wireless signal so maybe it's not getting the file fast on wifi
Validate Windows is not using the class driver by going to the usb pc, finding the printer, right clicking the printer(windows 7) clicking printer properties->advanced and looking at what driver is in use.
Or (Windows 10) clicking manage printer -> printer properties -> advanced
Try putting the pdf on a thumb drive and popping it in the printer. See if it prints quickly there.
Lastily update the firmware on the printer.