Dilemma: your printer adds a 1/4″ white border on your greeting cards. It looks okay but there are ways to add a more polished finishing touch.
In Photoshop, go to Image > Canvas Size and add an inch or more to width and height in White. Then use the Magic Wand (shortcut W) and click in the white border. Now Ctrl/cmd I to invert the selection and the marching ants should be around the photo area.
Edit > Stroke > 6 px > click in color swatch and you can click a color in your image to use. I use Inside to make sure it prints within my printer’s ability. If you choose outside you may lose part of your stroke depending on the width of your white border. This is called a keyline.
Here is the final look (the black line is just to show you the border)
You can add much wider borders of course and experiment with different colors.
For a detached keyline I create the stroke in a different way. Let’s say your image is 5×7 and you do not want to add canvas size, making cropping more difficult sometimes.
First, click on the padlock on your image layer. It will become Layer 0.
Add a layer filled underneath your image (Ctrl/Cmd and the new layer icon will add the layer underneath your selected layer. Edit > Fill > White.
On your Image layer – Edit > Transform > Hold down Shift Opt/Alt and pull a corner handle towards the middle slightly leaving a white border.
Use the Rectangular Marquee tool (M) and draw a box in the white area. Then Edit > Stroke > pick your color and size and hit okay. ( The outer border is to show you the whole card area. You do not add that.)