Magento

I know that if I want to add attribute to the pdf of invoice, I need to edit
Mage/Sales/Model/Order/Pdf/Items/Invoice/Default.php
and Mage/Sales/Model/Order/Pdf/Invoice.php

But how about if I want to customize the email of invoice that sent to client?
Can anyone show me the path? Thanks!

Hi,

I think these paths should help you:

app/locale/en_US/template/email/sales/invoice_new.html
app/locale/en_US/template/email/sales/invoice_new_guest.html
app/locale/en_US/template/email/sales/invoice_update.html
app/locale/en_US/template/email/sales/invoice_update_guest.html