There are 2 ways to revert your documents if you make a mistake. The first method is to simply undo your changes (Ctrl + Z or click the undo button) and then re-export or save. This however only lasts for the session you are working in so if you close your document or browser you won't be able to undo any further.
In this scenario, the only other way to revert changes in that document would be to use your cloud storage provider's file version control to restore or revert your file. Please see the links below to view the cloud storage provider's articles on how to do so:
OneDrive currently doesn't support non-MS Office file format history, so it's recommended to sync your files to an external backup. The above link to OneDrive explains how to do this. We recommend taking backups of all critical documents regardless of cloud storage provider.