You can use the Preliminary selection to open the right portion of the window.
In this mode, all invoice within the interval that you selected in the left portion of the window will be loaded. You can deselect the invoices that you do not want to print. At the far right you will see the invoice status when printing pro forma invoices. This is an example of the "Preliminary selection" method. To return to the left portion, just click the Cancel button.
When the right portion of the window is activated, you can also click on Preview in the Window functions or double-click on the invoice number to preview the printout.