As Rich stated,there are several ways to do this!
Here's another way. Building a template. This is similar to the guide and grid, just a different take on the technique.
We know that our image is 15cm x 10 cm. So create a document to that size.
The document serves as the Outer boundary
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We know that our border is 13.7cm x 8.8cm
Use the rectangle Tool to create an Inner boundary.
Center by hitting Cmd/Cntrl +A, use the Move Tool and the Horiz & Vert center alignment tools in the tools option bar.
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We want our image to be within the border constrained to the inner boundary.
All we need to do is to drag and drop our images. This method will open the image as a smart object. Or use FILE > PLACE EMBEDDED.
Then clip the image to the inner boundary layer via clipping mask.
You then use Free Transform on the image layer to adjust the image to fit within the inner boundary. Since this image was opened as a Smart Object,
you can always come back and make changes to the images size or position with ease.
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When satisfied with the fit, un-clip the image layer.
Save and print.
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Or leave it clipped and save with the border.
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Rinse and repeat by turning off the image layer (optional), and then dragging and dropping a new image above the the inner boundary layer (or the old image layer) and clipping.
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Note that the new (Clipped) photo will show in the document when it's the uppermost layer.
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