Get Shopping cart rule info in invoice PDF

Question

I would like to use shopping cart rule information in the invoice PDF. For certain rules I want to add some information in the PDF. How can I get these values?

Answer 1

I've found the following to work:

$order_ov = get_object_vars($order); 
$couponcode = $order_ov['_data']['coupon_code'];

Answer 2

$couponCode= Mage::getModel('sales/order')->loadByIncrementId(ORDERID)->getCouponCode();

You can then look up the cart rule info, using salesrule/rule model.