Changing the canvas size and scale with the Canvas Size inspector
Use this inspector to change the size of the canvas, how the canvas fits onto printed pages, or what kind of measurement units to use.
The Canvas Size fields control the width and height of the canvas. You can use any of the units available in the Ruler, or enter a number of pages.
Select Size is multiple of printer sheets to make the edges of the canvas snap to the edges of pages. This prevents the canvas from ending in the middle of a page.
If you select Auto-adjust the canvas size, the canvas will grow or shrink to fit the objects you create.
When you print, if Print canvas on one printer sheet is selected, the canvas gets scaled up or down to fit a single piece of paper regardless of its size on the screen.
The Orientation of pages can be portrait (vertical), landscape (horizontal), or can be taken from the settings in Page Setup.
Ruler Units The Ruler Units pop-up menu is where you set the type of measurement units you'd like to use for the current canvas. All of OmniGraffle's supported units are listed, with their standard abbreviations.
The actual size of your diagram does not change when you change the units; it is merely measured differently. The ruler and the inspectors display measurements in whichever unit you select here.
Units marked with an asterisk (*) can be used as canvas units. This means that when you set up a unit scale (see below), only these units can be used on the left-side "actual size" part of the equation. Any kind of units can be used on the right-side "theoretical size" part of the scale equation.
Unit Scale The Unit scale control can interpret simple expressions of scale. Several useful scales, such as 1 in = 1 ft, are available, and you can also enter your own scale by choosing Custom.
For example, say you enter 1 cm = 1 m. What was 1 centimeter on the ruler now becomes 1 meter, objects on the canvas that were 2 centimeters wide now become 2 meters wide, and so on. The units setting changes to match the second value in the equation.
You can also enter a ratio. Imagine that you enter 1:12. The ruler units stay the same, but objects on the canvas now claim to be 12 times larger than they were before you changed the scale.
To change the scale back to normal and treat the ruler and objects as "actual size", select Reset Scale from the Unit scale pop-up menu.
If you already have a scale set up and you conver directly to a different one, the objects change their actual size on the canvas to fit the new scale. For example, imagine you are working in 1 cm = 1 m, and then you convert the scale to 2 cm = 1 m. The marks on the ruler become twice as far apart as they were, and the objects on the canvas, staying true to the ruler, grow twice as large on the screen. You can get a new scale without resizing the objects by choosing from the Reset Scale To: section of the Unit scale pop-up menu.
By default, the very upper-left corner of a canvas is its origin (that is, the point where the rulers' measurements start from, where the coordinates are 0,0). To change the origin, enter values in the two Origin fields. (You can also drag the origin from the corner where the rulers meet.) The coordinates in the Geometry inspector are based on this origin point.