Good question! I tried searching for "picture," "show picture," "see
picture," "view," "display," and various other combinations with "graphics."
I suspect the only place this is discussed at all is in the Help topic on
the View tab of Tools | Options, but if you've gotten that far, you already
know the answer. That's why NGs such as this (and Web pages such as http://word.mvps.org/FAQs/DrwGrphcs/InvisibleGraphics.htm) exist.