Check the settings on your Printer... that's where you can do that... Word
doesn't control that.... your printer does. Many printers will not print to
the edge of the paper... so if you have a new printer... you may not be able
to do it any longer.
The printer driver is the key not Word. If you go to the printer setup, you
may have a setting for Borderless prints for certain page sizes. Then you
can select zero margins in Word and print to the edges.