This functionality lets you send invoices by bulk and at a later time, Joemeilak.

Once you choose this option, here's how you can send them:

1. Click Sales.
2. Go to the Invoices tab.
3. Select the invoices.
4. Click Batch actions, then select Send invoices.

I've got a reference about emailing or printing an invoice. 

If there's anything else we can do for you, please don't hesitate to get back to this thread.