To bring up the version history of any document, right-click on it and select "History."
This will bring up the History dialog that lets you browse through previous versions of your document.
In the left panel, you can browse through previous versions of your document. You'll see the time it was changed and who changed it. This is especially useful for a shared document. Once you select a version, the pane on the right will show you a preview of that version.
Click "Restore" to make the selected version the current one.