1. Draw a polygon (a fill) over top of the drawing window. Edit it to be roughly the size/shape you desire.
2. Select the frame and the polygon together.
3. Choose "set polygon as drawing frame", probably in the edit menu. (it has been awhile for me since using AC9)
4. The two will merge, and now you should be able to add points to your drawing frame and give it odd shapes.
Good luck!
JB
AC 21 (8002) & 22 USA
Mac OSX 10.14.5 on MacBook Pro 2.3GHz Intel i7, 16GB Ram, NVIDIA GeForce GT 750M 2GB VRAM, 500GB SSD