KeepSafe is a real-time backup tool that is designed to act as a safety net against accidental modifications caused by editing or other modifications to a file. It is not intended as a full scale backup solution, but rather to provide protection during those times between backups. You can let the program monitor a list of folders and specific file types within those folders, and whenever you modify one of the protected files it will automatically create a backup copy and maintain an archive of file revisions, allowing you to restore a previous version of the file if the need arises. You can configure the program to limit the number of revisions to keep, where to store them and also set other options to customize the backup behavior. The trial version is limited to monitor your My Documents folder.

The license of this software is Free Trial Software, the price is $29.95, you can free download and get a free trial.