Do you want to allow your customer to edit the product on the product pages of your store?
T shirt designer PrestaShop module can help you.
This plugin creates a button on the product page of store.
When a user clicks over it, a window will be opened to show the customization buttons.
Another great feature is that when a user insert something on the product, price will be auto updated there.
Therefore, user will know right at the cart page that exactly which product he is offering.