Magento – Add TAX pecentage (%) in PDF invoice summary

You can customize the invoice layout by modifying this file : Mage_Sales_Model_Order_Pdf_Invoice(app/code/core/Mage/Sales/Model/Order/Pdf/Invoice.php). Of course you need to rewrite the file properly.

Also take a look at these articles for additional info and examples:

1. http://www.atwix.com/magento/customize-magento-pdf-invoice-and-packingslip/
2. http://www.satollo.net/magento-how-to-sligtly-modify-the-invoice-pdf
3. http://www.magentocommerce.com/knowledge-base/entry/custom-pdf-templates/
4. http://www.magentocommerce.com/wiki/5_-_modules_and_development/orders/editing_an_invoice_pdf

Rewrite the model Mage_Sales_Model_Order_Pdf_Items_Invoice_Default and remove this

    // draw Tax
    $lines[0][] = array(
        'text'  => $order->formatPriceTxt($item->getTaxAmount()),
        'feed'  => 495,
        'font'  => 'bold',
        'align' => 'right'
    );

the model Mage_Bundle_Model_Sales_Order_Pdf_Items_Invoice and remove this:

            $tax = $order->formatPriceTxt($_item->getTaxAmount());
            $line[] = array(
                'text'  => $tax,
                'feed'  => 495,
                'font'  => 'bold',
                'align' => 'right'
            );

and the model Mage_Downloadable_Model_Sales_Order_Pdf_Items_Invoice and remove this

    // draw Tax
    $lines[0][] = array(
        'text'  => $order->formatPriceTxt($item->getTaxAmount()),
        'feed'  => 495,
        'font'  => 'bold',
        'align' => 'right'
    );