There's no built in way in word to create what you want, but here are some
options.
1. - Check your printer driver settings, some drivers have an option for
mirroring text documents when they're printed, so you may have have onr of
those.
2. - See if you can find a .PDF writer with the same option, I have the
PDF995 printer driver PDF creator and this has the facility to mirror text.
3. - Use a graphics program to create your text and then mirror it, you can
do this with Paint Shop Pro, and probably with Windows Paint too.