Rulers help you precisely position and size layers.
Do one of the following:
The rulers' preferences apply to all Pixelmator Pro documents. You can change preferences at any time, even if you’re editing an image.
The zero origin is the location of the rulers’ 0. By default, units increase from 0 in the upper-left corner of the image, but you can also change the zero origin to any other location on both the vertical and horizontal ruler.
Tip: Press and holdon your keyboard to automatically snap to rulers' tick marks as you're adjusting the zero origin rulers.
To reset the zero origin, double-click the area where the horizontal and vertical rulers meet in the upper-left corner of the canvas.