How to add Attribute reference to invoice

[Mictor2010]

I recently followed this guide http://www.prestashop.com/forums/topic/194927-15-how-to-add-product-reference-number-to-pdf-invoice/?hl=%2Breference+%2Binvoice&do=findComment&comment=1354505 to add a general product reference to the invoice however each attibute has its own reference number, is there a way to add this into my invoice sheet?