If the document is not saved in the client-side or server-side event handler, the Save button and a call to the saveDocument method have no effect.
When a user clicks the Save button or the saveDocument method is called, the Rich Text Editor converts the document's content to base64 and invokes the Saving event. Write the event handler to save the document on the client side. Set the handled property to true to prevent further processing.
Use the documentSaveFormat property to specify a format in which the document will be converted to base64.