From the Domainstab, click the domain. (If the correct domain isn't listed, choose it's subscription from the drop down menu in the upper right.)
Select the Websites & Domains tab.
Select the Backup Manager in the right hand menu.
Select Back Up.
Server Repository will be selected by default unless you have set up a FTP repository.
In Plesk 12, under the Backup Settings section select the radio button labeled Domain configuration and content. Leave the drop box the way it is.
In Plesk 12.5 under Backup Content->Type, select Full or Incrememental as needed. An incremental backup will only backup those files which have changed since the last backup. For this reason we recommend Full backups.
DO NOT select the Suspend domain until backup task is completed. Should the backup fail, your domain would remain suspended and inaccessible to your website viewers.
Once the backup is completed you can download it from the main backup screen by clicking on the Green Circle/Arrow icon on the right side of the backup listing.