To customize the text of a domain called example.com, perform the following steps.
Create a directory <domain-dir>/example.com
Copy <domain-dir>/en/i18n.properties to <domain-dir>/example.com/en.
This would be the default path of the i18n.properties for users in example.com domain.
Create directories for each supported locale such as en_US, ja, de_DE, fr_FR under <domain-dir>/example.com/ .