It sounds like you are trying to change the defaults from inside of Word.
Try going to "Start -> Printers & Scanners -> Printer -> Printer Properties -> Advanced -> Printing Defaults" and change it there instead.
And while you are at it, since it sounds like you are on the client printing since you are using word, change the "Start -> Printers & Scanners -> Printer -> Printer Properties -> Preferences"
Setting the Printing Defaults on a server sets the default on the client connecting to the share.
Setting the Preferences changes only the current client.