How to create custom field for print/pdf

Dears,

I am new to ERPnext.

1/I need to issue an Invoice with indication of the 5%TAX on total value and this value shall be written ‘in words’. I couldn’t find such existing field. When I use “In Words” field, it reflects grand total amount.
Please help how I can create it?

2/ Also can someone advises how to display currency in english in print/pdf format? It is showing in arabic letters.

Thank you for your advise.