On the Mac, you can just do COMMAND-SHIFT-3 to capture an image of the
screen into a file (it will be called Picture 0 in the main folder of
your hard disk; do it again, and you get Picture 1, Picture 2, and so on).

To print that out, you can open it with TeachText or SimpleText. If you
want just a part of it, you can select an area by dragging, then copy it
to the clipboard and paste it into Microsoft Word or some other program
that accepts pasted graphics. You may have to set TeachText's memory
partition to a larger value -- 500K or 1000K instead of the normal 194K.