Part Sales Orders - Update so Delivery Notes can be updated without raising an invoice

Would it be possible to be able to do a part sales order, without having to raise an invoice for each part order. Our clients only want one invoice when orders are completed. However this cannot be done, and we have to create a pdf delivery note for every part order, and then edit the pdf and manually change the quantities being delivered, and quantities still outstanding.

This takes time, and not everyone in the company has the subscription to PDF editor to do this, and this causes a lot of issues.