Rulers
The rulers, guides and grids help in achieving accuracy when it comes to laying out objects on page to give a sense of balance and order to page. The rulers help take measure of a layout.
Rulers, Guides and Grids help you to achieve perfect balancing for the various elements of your design. Rulers are visible along the left and top edges of the image rulers'. They help you measure a layout. The Zero point for both rulers is at the top left corner of the image.
To show the rulers select View > Rulers.
You can choose from different units of measures, such as pixels, inches, centimeters, millimeters, pints, picas and even percentage. To change the unit, position the mouse over the units on one of the rulers. Right click and choose new units of measure. Or double click the ruler and change the unit in the preferences window that opens.
