SINGLE Invoice for 2 or more orders in magento

It is possible to make an invoice for 2 or more orders at the end of the month? I can see only to option to make invoice for every order.

If not, I'm looking for an extension to calculate the to开发者_JAVA技巧tal in the printed PDF for 2 or more invoices.

Are you looking for one page for each invoice, or for an invoice that combines all orders? The mass action menu (the one where you check boxes in the order list and then use the dropdown to actually execute an action) will let you print multiples at once, and will concatenate each of them into the PDF.

If you want to combine the orders, you'll need to write some code of your own to coalesce the order details together before printing them.

The file you want to clone and work off of is Mage_Sales_Model_Order_Pdf_Invoice. All of the Order_Pdf_* classes implement Mage_Sales_Model_Order_Pdf_Abstract, so make sure you base off of that class as well.

On the controller level, look at Mage_Adminhtml_Sales_OrderController::pdfinvoicesAction, for code that should aggregate the orders and generate a PDF.