Few days back I was supposed to integrate pdf library to generate invoice pdf instead of Zend Pdf. For that I tried to override the Invoice print action . Below are the steps you need to follow to override magento admin controller.

STEP 1 : Create simple module  Eg TW_Printinvoice , here TW is the namespace and Printinvoice is the module name.

config.xml : This file will be placed under app/etc/code/local/TW/Printinvoice/etc

[codesyntax lang=”xml”]

<?xml version="1.0" encoding="utf-8"?>
                        <TW_Printinvoice before="Mage_Adminhtml">TW_Printinvoice_Adminhtml</TW_Printinvoice>


Step 2: Create the controller file under the path :app/etc/code/local/TW/Printinvoice/controllers/Adminhtml/Sales/Order/InvoiceController.php

[codesyntax lang=”php”]

require_once 'Mage/Adminhtml/controllers/Sales/Order/InvoiceController.php';
class TW_Printinvoice_Adminhtml_Sales_Order_InvoiceController extends Mage_Adminhtml_Sales_Order_InvoiceController
    public function printAction()
	// write your code here 

    public function pdfinvoicesAction(){
        // write your own code


Once you add this module in magento , login to Magento admin  > Go to Sales > Invoices

Click any of the invoice to view , in the detail page you will see print , once you click that it will call your print method instead of default magento print ..

Thats it …