paper size and tray auto select

Hi,

I just bought a C7020MFT printer and one setting has puzzled me for days. here is the problem:

tray 1:A4 dedicated/auto select

tray 2: A3 dedicated/autoselect

when printing pdf files from acrobat reader the normal process of specifying papaer size via page setup at bottom of the printing window has no effect on the actual paper size printed. To get the right size paper, it has to be specified in the printer properties at the top of the print window. This happens to other app as well such MS Word/Exel. I just cannot get the printer select right tray/paper-size according to the software seting as we did with a Xerox workcentre. Any one can shed light oon this?

thanks.

Daoning