Adding notes can be done by two ways, manually or automatically.
1. Manually
Go to Sales Order submenu from Orders & Deliveries module and click on an order.pro
Scroll down and add text to Internal Notes, those notes will appear on the order's PDF.notes
2.Automatically
Go to Sales Order submenu from Orders & Deliveries module then choose Sales Order Settings from Three.notes
Click on Default Note, select for what language you want to add the note then after you write it click on Save.notes4.png