artboard size in Illustrator

Adobe Illustrator is yet another program that I have never fully grasped. 

But here's how to change the size of the "Artboard" (corresponding to the "page", and holding the artwork that is printed or saved as PDF).

File > Document Setup > Edit Artboards

You should get a drag-able box. 

Useful if you want to scale a 6-inch image by 1000% for a banner.