There is a backup possible for all pages and files ( not forum threads and posts!) on
Site Manager Backup.
Here you can start a backup file and decide which zipped "format" you want the backup file to have: "tar.g"z or "zip" (for smaller wikis).
After some time you shoudl control if the backup is finished and than DOWNLOAD the file to your local disc.
Otherwise it makes no sense - the backup files on the wikidot storage are disappearimg after some time..
Here I have included the page of the Site manager menu for better understanding:
This is the Backup Screen on the Site manager ( page admin:manage ):
To CREATE a backup file ( select by drop down menu .zip or tar.gz ):