Converting a A4 page to A6 size in CS 2

Hi.
I have a large document made in presetting for A4 in CS2.
A4 is 297x210mm and A6 i appr. 149x105mm
I need to convert this in to a A6 document, print quality.
All I can find is the possibilities you have in the presetting.
Hope that someone can help me:)
Br. Jan