I'm not sure if 5LE has this, but try Filter/Other/Offset. set it for about half the pixel dimensions of your page. That will show you where your seams are. Now use the clone tool to cover over your seams. Stay away from the edges of the image or you will create new seams. Run the offset filter a few more times at random settings to make sure you've gotten all the seams. "Define Pattern" usually won't show up in the menu unless you've made a rectangular selecton with no feathering.