Master Canvases
A master canvas is a special kind of canvas which acts as a base for any number of regular canvases. The contents of the master appear beneath the contents of each canvas that depends on it. The dependent canvas also receives the master's canvas size, units, grid, and other settings in the Canvas inspectors. Manual guides on the master also appear on the dependent canvas.
If you use the Canvas inspectors to manually change some aspect of a dependent canvas, such as canvas size or grid, the canvas becomes independent with regard to that setting. The canvas still depends on the master for its other attributes, and you can reset all dependencies with the command Edit ‣ Canvases ‣ Synchronize with Master Canvas.
The master canvases are listed in the utility drawer. To open the utility drawer, select it from the View menu or click its toolbar icon. Click the Canvases tab at the top of the drawer for a list of the canvases in your document. Each master canvas has a disclosure triangle, a preview, a title, and a color well.
To work with a master canvas, click its entry in the Master Canvases list. The master canvas appears in the document window, where you can add and edit objects.
To apply a master canvas, drag it from the Master Canvases list and drop it on a canvas in the Canvases list below. You can apply a master canvas to as many canvases as you like, but each canvas may have no more than one master canvas applied to it at a time. To detach a canvas from its master, select the canvas and then use the gear menu at the bottom of the canvases drawer to Remove Master Dependency.
To rename a master canvas, double-click its name in the list.
To change the color of a master canvas, click its color well in the list.
To create a new master canvas, first select an existing master canvas. Then click the plus button at the bottom of the canvases drawer.
To delete a master canvas, select it and then click the minus button at the bottom of the canvases drawer. Any OmniGraffle Pro document needs at least one master canvas, so you can't delete the last one.