When creating or editing a sales invoice you can choose to show both the invoice and delivery address on the invoice PDF, however, both addresses must be filled out for the contact you are invoicing.

Step 1.

Navigate to Contacts > Customers.

Step 2.

Click the Edit Contact link beside the appropriate customer. 

Step 3.

Fill in both the Invoice Address and Delivery address.

Step 4.

Create a new invoice for this customer.

The invoice should now display a checkbox to display both invoice and delivery address just below the summary box.