That you can bulk post invoices and bulk email/print emails for your customers.
On the Order Search page if you have the status filtered to Unposted, you will be given access to a Post button. If you have the system set to automatically set the invoice date and you are not using the approved total feature then you can utilize the button freely but if you are using either feature than you will have to set those fields first (lets face it, it would defeat the purpose of those features otherwise).
If you have a lot of invoices that need to be sent or resent to a customer, you can do that in bulk. You can either hit View All for the Orders on the Customer page or on the Order Search page you can search by customer number and that will bring you up an invoice split button. Select the invoices you want to print or email and use the split button to take the action you want.