Create additional notes on invoices

Hello, I have a special module to request for. I need a module which can add additional notes on each order from our backend. And the notes will appear when the invoice is being printed out. The notes could be added on the individual order through the magento back end and this notes will be saved for that particular order which will also be appeared on the invoice related to that orders. This notes is important if there is anything that i would like the customer to know. I need someone who can do this fast and efficiently.