Hello Toll-Lady,
Welcome to the HP Support Forums.
I understand you are looking for a way to reset your HP ENVY 4500 printer to try and resolve the freezing issue when trying to make a copy. Before a reset is done on the 4500 I would like you to try a couple things first.
Try connecting the printer to a direct wall outlet if it is connected to a surge protector to insure the printer is getting the needed power. This HP document: Issues when Connected to an Uninterruptible Power Supply/Power Strip/Surge Protector explains the benefits.
Try as well doing the updates on the printer to insure the printer is functioning 100%, this HP document: Getting the Latest Firmware and Printer Updates will show you how to update the ENVY 4500.
Thanks,