Print button at order check out or redirection at order detail

[clementine]

All is in the title.
I'm under Joomla 2.5 and virtuemart  2.6.10.

I'd like to add a print button to permit to my client to print order details or create a redirection to a order detail page (which can be easily printed).

I know that something has to be modified in the php file "order_done" but i don't know what.

Please, help me ! 

[GJC Web Design]

put a link well labelled on the order done to the order details?