The Reveal Canvas command resizes the image canvas to reveal any parts of the image hidden beyond the edges of the canvas. This can happen when reducing the size of the canvas or cropping nondestructively.
Reveal parts of an image beyond the canvas
Choose Image > Reveal Canvas (from the Image menu at the top of your screen).
Click in the Pixelmator Pro
toolbar, then choose Reveal Canvas.
Choose the Crop tool and double-click inside the crop box.