Magento – How to Add VAT or Business number on .PDF invoice

Take a look @

• Customize Magento PDF Invoice and Packingslip
• Edit an invoice PDF

You will need to rewrite order_pdf_invoice (or copying it to app/local/Mage)

<models>
    <sales>
        <rewrite>                    
            <order_pdf_invoice>Atwix_Printedorders_Model_Invoice</order_pdf_invoice>
        </rewrite>
    </sales>
...
</models>

You can try entering this code in class Mage_Customer_Helper_Data:

protected function _createVatNumberValidationSoapClient($trace = false)
{
    $options = array( 'soap_version'=>SOAP_1_1,
        'exceptions'=>true,
        'trace'=>1,
        'cache_wsdl'=> WSDL_CACHE_NONE,
        'user_agent' => 'Mozilla',
        'proxy_port' => 80);
    return new SoapClient(self::VAT_VALIDATION_WSDL_URL, $options);
}