how to print with correct size?

[Jacek Popławski <jpopl interia pl>]

It should be simple, but I've never do it...

Let's say I need to print rectangle of size 6 cm * 9 cm. 
How can I do it with dia? 

I can draw 6x9 rectangle, then print it, but picture will be scaled up.
What should I do to avoid scaling?

PS. Of course I need to print more complex picture than single rectangle, that
is only an example.