1. Will these things go through your printer? -- with some printers you'd
run a risk of damaging the print head when it meets the edge of the tab; and
most printers use the edge of the paper to keep the paper straight, so
alignment might be a problem if you print with the dividers at the bottom.
2. Can your printer handle that page size? -- ie, legal plus the depth of
the tabs.
3. Can your printer actually print on to them? --probably not if they are
made of polyethlyene
If you're OK on the above points, create a document in Word that's the size
of the divider including the tab. Position a textbox for the divider text,
and away you go.