You can see how the pages will print in the layout preview here - http://www.viovio.com/products/layout_preview.php?products_id=128351 For books 6 x 9 or larger, you will want to look at the red crop guide and for anything smaller, look at the pink. Anything outside of the designated crop guide may get trimmed in production. We have a page with all the info you need to know about setting up your Aperture file here - http://www.viovio.com/wiki/Apple+Aperture
I hope this helps! Please contact us at firstname.lastname@example.org if you have any further questions!