Hi user_questions.
Being able to customize your email templates is one of the ways QuickBooks Desktop lets you add your own personal touch to what your clients see. I'd be happy to help you go over how to update the email template.
To explain why it was different in one version of QuickBooks compared to another would be that the customize email template changed in later versions of QuickBooks. The new template allows customers to have more freedom on what they can change when emailing customers. For 2013 there isn't a way to change what a customer can see beyond what is included in that screenshot. If you wish to modify this further I recommend either getting your client to upgrade their QuickBooks to a newer version by purchasing QuickBooks Desktop 2021 at a number of retail locations. Saving the PDF and attaching it directly to an email which bypasses QuickBooks entirely or looking into a third party app that can email your invoices out for you.
You can save an invoice as a PDF by opening the invoice in question, selecting Print and Save as PDF. Once this is done create an email in using your email provider and attach the PDF to send. If you want to look into third party apps you can check out our third party apps page.
If you have any questions let us know and we'd be happy to help.