At the current time, there is no way to automatically send multiple copies of digital invoices to a customer. However, I have customers asking me to send more than one copy of each invoice to their organization. So I have to remember to select an additional contact person whenever I'm sending out invoices.

Please add a new field (call it CC or something similar) to the Contact Persons screen that, when selected, will tell the system to send an invoice to the primary contact AND to each secondary contact that has the CC field selected.