You can buy the unassembled wire cubes. Mine are the Whitmore Storage Cubes from Target. Use 5 pieces to create a cube. Then, simply add shelves with the remaining wire squares. You can stack your cubes in a variety of ways. See how I did mine here:

You can use a variety of things to hold the shelves in place (like twist ties or zip ties), however, I find using electric tape works the best and looks the best. See how I did that here:

This is a very cost effective way to store, display, and organize all that 12 x 12 paper!!!