Is there a keyboard shortcut to switch between open documents?

Hi Floyd! Although this is an old thread, it is actual for me as I have just decided to search for the same question after years of suffering the same issue with word for mac. I see that although Peter´s comment is correct, the one´s that use different language keyboards (from English), such as myself that have an american keyboard set to spanish (and thus the key location of the tilde-"`" sign is not apparent) cannot utilize this shorcut. The way around this is pretty simple - you have to open System Preferences (under the apple logo on the top menu), then click on Keyboard and on the window that appears go to the Shortcuts tab, make sure that the "Move Focus to Next Window" option is enabled. You can see on the left side of the option, effectively which key combination will do the trick (mine is command + "`", but i´m guessing other languages might not have this specific combination as the tilde sign might not be present in languages such as finnish, german or chinese, guessing). Now the only question is being able to locate where in you keyboard that sign is hidden. In my case, spanish option on an american/english mbp keyboard, the tilde sign is under the right bracket key on the right side of the keyboard, i know this from using it to add accents to spanish vocals, but you could also look for it in the Keyboard Viewer under the Input Sources tab (also in keyboard preferences). Unfortunately for some strange reason, i find my Keyboard Viewer not working interactively (showing signs to keys relationship as i press the keys) under Mac El Capitan iOS. Hope this clears the issue and helps people with the same question. Cheers. Demian