The usual problem is to do with aspect ratios of the image versus the paper.
A typical Point and Shoot camera produces an image with an aspect ratio of 4:3. (Width to Height).
A typical paper size is 6" x 4" which is a 3:2 ratio, so the 4:3 wont fit exactly.
You should consider the image format and paper format you are using and if necessary crop the image, using something like Photoshop, to the same aspect ratio as the paper you intend to use.
Colin