This is not a question. It's a sharing.

I was having trouble with Duplex printing, similar to the
threads posted on 7/12 and 7/21. While we were all on the
right track, there is a slight error in the sample code
posted on the Microsoft Knowledge Base article 230743.
This error was hinted at in one of the threads, but to
really undertsand why, take a look at
http://word.mvps.org/FAQs/MacrosVBA/SetDuplexOnOff.htm

Suddenly it all made sense. Oh, and now my code works,
too.