Hi,

You can use the DB backup and restore it on your SQL server. The documents are stored in CMS_Document table, but there are lot of foreign keys e.g. in CMS_Tree table and in the document type tabel, so it is recommended to restore the whole DB. Or, if the backup is older, you can create new instance of Kentico CMS and point it to this newly restored DB and export appropriate documents and then import them to the live site.

Best Regards,
Juraj Ondrus