There are a few ways to change the artboard size in Illustrator. The first way is to open the Preferences window and select the “Artboard Size” tab. There you can set the width and height of your artboard. The second way is to use the “Command+Option+N” keyboard shortcut to change the artboard size. The third way is to use the “Command+Option+V” keyboard shortcut to create a new artboard.
