maintaining object's size-proportion during printing

[Nicolas Cueto]

Hello all,

I'm being somewhat lazy here.

If a card of as yet unspecified size shows
a 5x5 grid of image objects, with the size
of each image object being a perfect square,
and the printout paper size is to be A4 (or B5),
how would I ensure when the card is printed
out that the square-shaped image objects
do not become rectangle-shaped?

A solution, or perhaps llinks to a tutorial or
some sample stacks, would be a great help
and time-saver -- not to mention paper-saver,
too.

Thank you.

--
Nicolas Cueto