transaction_controller.rb

def show
    prawnto :prawn => { :page_size => 'A4',
                        :left_margin => 40,
                        :right_margin => 30,
                        :top_margin => 40,
                        :bottom_margin => 30},
                        :filename => "invoice_{@transaction.id}_customer_{@transaction.customer_id}.pdf"
    render :layout => false
end