Each time you save a document, you can automatically retain a copy of the last saved version. That way, if you change your mind about edits you made, you can go back to (revert to) the backup version of the document.
The best way to create backup versions depends on which version of OS X you’re using. OS X Lion (v10.7) and later automatically saves a snapshot of your document every time you save. You can access an archive of all of the previous saved versions at any time. To learn about accessing and using past document versions in OS X Lion, see Finding an Archived Version of a Document.
If you’re using Mac OS X v10.6.x (Snow Leopard) or earlier, you can set up Pages to automatically create a copy of the last saved version of your document. You may also find this useful if you’re using OS X Lion, and you want to save a backup version of your document on another hard disk on your network.
Choose File > “Save a Version,” or press Command-S.
Choose Pages > Preferences, click General, and then select “Back up previous version when saving.”
The next time you save your document, a backup version is created in the same location, with “Backup of” preceding the filename. Only one version—the last saved version—is backed up. Every time you save the document, the old backup file is replaced with the new backup file.