How do I resize the workspace to original size

I feel stupid even asking... I clicked on "something" in the left side menu and my workspace shrank to a small window. Subsequent clicking hasn't re-sized my window yet.
Note to self - no haphazard clicking!
Thanks!
Comments
On the menu bar on top: File > Document Setup. Or [Ctrl]+[Alt]+[n] or [Alt Gr]+[n].