There are many instances when you may want to add a digital mat or border to your image! You may want to do so just because you like the way it looks or if you want to mount the print and then also frame and mat it later. Adding a digital mat ensures that when you put it in a larger frame, the image won't have to be taped to the mat or be vulnerable to shifting over time.
Photo Credit: Caitlin Nightingale Photography
Step 1: Crop your image.
To start with, crop your image to the size you want it to be without the border @ 300ppi. In this case, I'll be ordering a vertical 11x14, but I want the actual picture to be 8x10, so I'm cropping and resizing the file to 8x10 @ 300ppi.
Step 2: Add your border.
Click on "Image" up at the top of Photoshop and then click on "Canvas Size." This will bring up the Canvas Size dialog box where you can format the border you're adding. Up at the top, it should tell you how big your current image is. Below is where you're going to choose your new size. Make sure the "Relative" box is unchecked and then put in the desired width and height of your image with the border. I want an 11x14, so that is what I've entered. You'll also want make sure the "Canvas extension color" is set to the color you want your border to be. Then click the "OK" button.
Step 3: Admire your digitally matted image.