In order to setup invoice printing:
Go to Setup → Bill Settings.
Enable or disable the available options, such as:
A5 Print
Show/Hide Staff Name
Other available invoice fields
Thermal Printer Settings
If you are using a thermal printer:
Open the Print Preview for the invoice.
Go to More Settings.
Select the required paper size, such as 80 mm.
Set the print layout to Portrait.
Save or apply the settings before printing.
Note: The available invoice settings can be customized, but the overall invoice layout is fixed and cannot be redesigned.