Your Mac saves every version of documents as you work on them, not just your most recent save. That way, you can return to a version of the document you worked on days, weeks, months, or even years ago. It's an under-appreciated feature for those of us on macOS, but one we take for granted for cloud-based documents like Google Docs.
To access these previous versions of a file, you just head to File > Revert To > Browse All Versions. This pulls up a Time Machine-like mode, which lets you flick through all previous versions of the document, and choose one to restore to. This works whether the doc is saved to your Mac or iCloud Drive.
Even if you don't actively restore previous saves of your macOS documents, you probably don't want to unnecessarily lose that data. Unfortunately, that's what's happening right now due to a bug in macOS 14.4. As highlighted by Howard Oakley of The Electric Light Company, it all has to do with how you manage those files between your Mac and iCloud Drive.
When you save a document from, say, Pages to your iCloud Drive, you may also keep a version of the file locally on your Mac. The beauty of iCloud Drive, of course, is that you can delete local files off your Mac while preserving them in the cloud. So, you might hit Remove Download on the file on your Mac, trusting that the file can be retrieved at any time from your iCloud Drive.
However, as it turns out, when you do this in macOS 14.4 with Optimize Mac Storage enabled, all versions of the file but the most recent save are deleted. When you try accessing the file again, you'll only be able to see how you left it last: Hitting Revert To will still pull up the time machine mode, but will show no past versions to restore.
If you're running macOS 14.4 on your Mac right now, you can replicate this bug in a program like TextEdit. Start a new file, enter some text, save it to your iCloud Drive, enter some new text, and save again. If you go to File > Revert To > Browse All Versions, you will see as many versions of the test file as you've saved. Now, head to your iCloud Drive in Finder, right-click on the TextEdit file and choose Remove Download. The file will show it is now only in the cloud. Open the file, which should redownload to your Mac, then head back to the Revert To option, where you will find no previous versions to access.
Since this is a problem only in macOS 14.4, Apple will likely patch the problem in a future update, perhaps sometime soon. However, you don't want to risk losing your previous versions in the meantime.
For now, it might be best to avoid saving documents to iCloud Drive, at least the ones you don't want to lose previous versions of. However, if you can spare the storage space, disabling Optimize Mac Storage will also help, since the bug doesn't seem to kick in with this feature turned on. You'll find the option in Settings > General > Storage.
