Yes, this a super easy way of doing this. All you have to do is hit Cmd-5 (or if you prefer the mouse, Documents/Snapshots/Take Snapshot). You will hear a camera shutter click, and when you hear that you know you’re safe to rampage through the text. But the first time you do it, you’ll no doubt want to verify it works, so click the blue ‘i’ button in the toolbar to open the Inspector. It will slide out on the right; at the bottom click the icon of the antique camera, and check the entry that has been logged in the top portion of this pane. If you click on it you should see the text of the current document in the preview area. This is uneditable, and not counted by any session tools or the total word count.
Try deleting a word, then hitting the “Compare” button. That’s how that works. If you ever want to roll back your changes, you can use the “Roll Back” button to simply jump back in time to this spot, or you can copy and paste the bits you want to revert by hand.
That is pretty much all you need to know to use it, but for full documentation, see §15.6 (pg. 221) in the user manual PDF. There are numerous options, including the ability to automatically snapshot every single piece of your draft that you’ve touched since the last manual save, when saving, taking snapshots with a title so you can remember what you took it for, and so on.