Which of the following shortcut keys is used to switch from one word document to another open word?

Ctrl+Shift+F6: switches to the previous document window when more than one document is open.

Some important shortcut with F6:
- F6 alone: switch between the document, task pane, status bar, and ribbon. In a document that has been split, F6 includes the split panes when switching between panes and the task pane.
- Shift+F6: switches between the document, ribbon, status bar, and task pane.
- Ctrl+F6: switches to the next document window when more than one document is open.
Alt+F6: moves from an open dialog box back to the document, for dialog boxes that support.