This extension provides a "Print Invoice" button on the Admin Orders view screen which opens a prinatble html page with the order details. You have to set up your computer for printing, or PDF ...
/pdf-invoice-generator │ ├── app.py ├── requirements.txt ├── README.md ├── templates/ │ └── index.html ├── static/ │ ├── style.css │ └── screenshots/ │ ├── UI_Invoice_Form.png ...