DI - Creating an invoice based on a delivery

What's the easiest way of creating an invoice based on a delivery? Is there a method in the SAPbobsCOM.Documents object that I can use to convert, or do I need to create two document objects and copy the value of each property accross?

I noticed the DI SDK help mentions a .Net code sample called "Order and Invoice" but I don't seem to have it install - can anyone tell me where I can download thing from?

Thanks