Display additional products/items on an invoice if set as a kit! (IF SOMETHING COMES SEPARATELY OR IS A FREE ITEM WITH THE MAIN ITEM)

Display additional products/items on an invoice if set as a kit! (IF SOMETHING COMES SEPARATELY FREE ITEMS) We sell products here where some times they come with a separate free items which we create as a products and give a pick bin but cant seem to add to the additional product as a kit so when you sell the main item it needs to have the free part as well on the pick sheet and invoice. Is this possible