How do you change the map size on polyworks?

ctr+a, Q, with Ctrl drag holding corrner (best with Shift too)

dosent work..?

Choose move tool, hold control (Your cursor will change). Grab the edge of the box that appears when you select something (The bottom right for best results, although it depends on which way you want to stretch it), and move your cursor around while holding down the left mouse button. Wallah, its resized!
If you want to keep the same scale, hold shift while resizing.