Signatures
In book binding, Signatures make up the body pages of the book. They are typically large papers that are printed, folded, and trimmed down to get the final pages, stitched along a binding edge.
Laidout lets you define the folding pattern by simulating the folds right on screen. After a folding pattern is defined, then you decide how many signatures to have in your book. There can be any number of signatures stacked up either next to each other, or inserted into other (folded) signatures.
A binding edge can be on any side of the page, on the left or right for typical books, or on top for calendars, or on bottom just for kicks.
You can see how this works in action on the How to make booklets page.
