As far as I am aware, you can only scale on Pepakura Designer, not Viewer. If you want to scale on Designer, Click 2D Menu - Change Scale. This bring up 3 options: "Increase Scale 10%", "Decrease Scale 10%" and "Scale Factor..." which gives you total control of scaling. Hope this helps. NOTE: You may have to buy Pepakura Designer 3 to use it's functions and save your changes.