Before and during checkout, a lot of customers would like to clarify the order details. Users might have the additional information they want to convey. In that case, the shop owner will undertanding better the customer's requirements. In this case, we should have a function which allow customers to attach the files to a purchase order right during a checkout. Here's a solution for the adding files on Magento 2 checkout page. The Order Uplaod Extension for Mgaento 2 allows uploading files for each product the customers buy. The attaching process is powered by Ajax and does not need to reload the page.With this extension, the user can attach files to order not only on the checkout page but on the order view page as well.