Constraint and rule-based page layout

Technologies are described herein for laying out content. Constraints and rules are defined for one or more content objects. The constraints are utilized to lay out content objects on a canvas. Content is received for one of the content objects. The constraints and rules for the content object are utilized in an attempt to fit the content to the selected content object. If the content cannot be fit to the selected content object, the rules are utilized to modify the constraints for the other content objects and the layout for the canvas is regenerated. If the available content cannot be fit to the content objects on a page without overflowing, one or more additional pages are added to the canvas. Once the additional pages have been added, the content objects are laid out and content is fitted to the content objects across all of the pages.