Backup files

Backup file is a feature built in the Application Kit of Mac OS X. It is not activated, but you can activate them by using the terminal application to enter in the command line
defaults write "iTeXMac" "iTMKeepBackupFile" "YES"

To retrieve the original state, enter
defaults delete "iTeXMac" "iTMKeepBackupFile"

More friendly user interface will be available once the preferences user interface is implemented.