You can download new language packs from Parallels site and install them to the control panel. The number of languages you can use with your control panel depends on the license key you purchased. The control panel will alert you when you attempt to install more languages than allowed.
To view the interface languages installed in the control panel:
To select a new default language for the control panel:
To install a new language pack:
Download the required language pack file from Parallels web site and run it. The installation wizard will install the language pack in your system, enabling you and Plesk control panel users to choose the corresponding language during the login or on their personal settings page.
To uninstall a language pack from the control panel:
If the language pack you have just removed is used by some other users, their interface language will be automatically set to the default language pack. The default language of the Plesk distribution package (en-US) cannot be removed.