Copying an object from one image and pasting it into another is probably one of the most fun things you can do with an image editing app like Pixelmator Pro. And it’s a great thing to learn because it’s an easy way to get the hang of a few basic but fundamental image editing techniques.
The first step is selecting the area of the image you’d like to copy. One of the best tools for making quick selections is the very appropriately named Quick Selection tool. To choose it, you can simply click 
in the Tools sidebar. Or press the key on your keyboard.
To select an object with the Quick Selection tool, all you need to do is paint over it. When you move your mouse pointer over your image and start painting, you’ll see a yellow overlay showing you which areas will be selected once you release the mouse.
Now that you’ve released the mouse, the black and white marching ants show you which areas are currently selected. Don’t worry, you don’t have to make your entire selection in one attempt! If you’ve selected a little too much or missed any areas, you can change the selection mode in the Tool Options pane just to the right of your image.
Change the selection mode to Add, then paint over the areas you’ve missed to add them to your selection. To remove any areas you didn’t mean to select, use the Subtract mode. There are also keyboard shortcuts you can press to turn on each mode temporarily — press and hold the key to temporarily use the Add selection mode, the key to use Subtract, and the and keys together to use Intersect.
Selection Modes
NewAlways creates a new selection, clearing any previous selections.
AddAdds any new selections to your current selection.
SubtractSubtracts your new selections from your current selection.
IntersectKeeps only the intersecting areas between your new selection and the current selection.
When copying an object and pasting it into another image, it’s a good idea to soften the edges of the selection a little. This is where the Refine Selection tool comes in handy. Softening the edges of the object will make it blend in better with the new image.
With the Quick Selection tool active, click the Refine button at the bottom of the Tool Options pane and drag the Edge Softness slider to around 25%. Now, the edges of the selection are softer and, when you copy the object, the edges of the object will be softer too. Click Apply to apply your refinements.
Refine Selection
Smart RefineTurning on this option refines the selection automatically, snapping the selection border to any nearby edges.
Edge DetectionAdjust the sensitivity of the Smart Refine tool to edges in the image.
Shape RoundnessAdjust how much to round the shape of the selection.
Edge SoftnessAdjust how much to soften the edges of the selection.
ExpandChange the size of the selection.
To copy the selected area, choose Edit > Copy (from the Edit menu at the top of your screen). Then, open up the image into which you’d like to paste the object and choose Edit > Paste.
To position and resize the object in the new image, you’ll need to use the Arrange tool. Click 
in the Tools sidebar to select it or press the key on the keyboard.
To move the object, simply drag it on the canvas. To resize it, drag one of the white squares around the object.
Tip
To move only the selection outline without moving the selected area of the image, drag it using any of the selection tools. To move the selected image area, drag the selection using the Arrange tool.
And there you have it. These are the basic steps for copying over any object from one image to another but you can also combine these techniques with other tools, for example, the Color Adjustments tool to adjust the colors of specific areas or the Effects tool to add effects to a specific area of an image.
