Once you have confirmed a number of orders they will appear in in a list on the Orders Pending Submission to Warehouse page.

To get to this page, go to the Orders tab, see Pending Deliveries in the lefthand sub-navigation.

On the Orders Pending Submission to Warehouse page, select all orders you wish to push to download as a single PDF. At the bottom of this page is a With Selected button, from this dropdown click Download to PDF - Single File. This will drop a single PDF containing an invoice for all of the orders selected to your downloads folder.