Hello I need 3 Inch invoice Template i need to use in Carbon Printer. Can anyone guide me ? How to Custom edit the Template ? or if you have a exiting Template it helps me lot 
I cannot realy help you building the template but maybe give some hints that could help;
With css @page you could possibly change the layout of the page. See: https://mpdf.github.io/paging/using-page.html
You can make a css override in the file custom-pdf.css located in assets/core/css
Hey hi. The same question even I had. But you have to guid me to change only document size to me I have changed styles for my requirements. Now the problem is that I am getting A4 size and if print in 3/8 printer I am getting brakes every page. So I need my invoice to be generated as hight into 3* A4 hight