if your paper is 12x12 and you want to make it into a 5x7 or 4x6 or any rectangular size, what I do is go use the scale tool to shrink the paper down to 7x7 or 6x6 or whatever the longest measurment will be and then cut off the exess. So if I want a 5x7 card, I would make my paper 7x7 and then use my rectangular selection tool to crop off 2 inches from one side, which then make the paper 5x7. You could just select a 5x7 pice of the paper also. I like to shrink it down first because then you see more of the pattern on the card. Hope that made some sense!
