There is a commercial product out there for Microsoft Word which makes this very common problem very easy to solve. It is called Tray Selector. You can download a free 30 day trial at
www.trayselector.com.
We used it with great success. It lets you setup toolbar or ribbon bar buttons and for each one you can configure a printer trays and a printer. This means in a single click you can do things like print a copy to headed paper or for example print a draft copy to plain or pdf. You can setup multiple copies and it copes very well with duplex and other types of printers.
Don't want to sound like an advert for the product but well worth checking out in my opinion.
Regards