you need :
1) $crud->add_action('Print form', '', '','ui-icon-image',array($this,'print_a_form'));
2) a function "print_a_form" like
function print_a_form($primary_key , $row)
where you can call a method (that you need to write) to get the form data based on $primary_key for example,
and then call a view (that you need to write) to show the data as you like and show also a print button that print what you see in the view.
2) function to call from add_action
3) method to get the data
4) view to show the data and print button
instead of point 4, remember that you can see the data already inside grocery crud, so you can directly insert the print command inside the function at point 2, after you got the data you want
Hope this can help you go in the right direction. Then you need to practice.