How can I add fields to the product details on an invoice, order or quote?

How can I add fields to the product details on an invoice, order or quote?

I use Zoho since several years, but allways i find a problem that now is really importante to me to solve!
On the product details area, I don't know how to add fields!
I like to had a field in the lines of the product details, like imagine "quantity in liter" and "quatity in boxes"

Waiting for help

Regards
Pedro