Taken me age to figure out how to remove the Tax column from the magento PDF invoice.

I’ve made all my changes in a local version of the Magento core code as described here.

The two files you need to edit are:

1. To remove headers: /app/code/local/Mage/Sales/Model/Order/Pdf/Invoice.php
2. To rmove the tax from each individual line item /app/code/local/Mage/Sales/Model/Order/Pdf/Items/Invoice/Default.php

Hope that helps

Simon