There is a View Helper availabe which allows you to use translations in your document editables.
Example: Translation of options of a select editable
(view script) ... <?= $this->select("select",array( "store" => array( array("option1", $this->translateAdmin("Option One")), array("option2", $this->translateAdmin("Option Two")), array("option3", $this->translateAdmin("Option Three")) ) )); ?>
After adding a new translation, the document needs to be loaded once in edimode. This adds the new translation keys to Extras > Admin Translations where all extra translations can be edited.translateAdmin