Ever notice that typical paper sizes don't match the size of the images coming out of our cameras? It happens quite a bit, especially if you print 8x10s - you'll notice you always have to crop part of the photo so it fits on the paper. Photoshop has a feature that can help out, called Content Aware Scale. It lets you scale (move and stretch) the image to fit a certain size, but also lets you tell Photoshop what parts are important so it doesn't mess with these areas.