Creating the order, the customers like to clarify the order details. Users might have the additional information they want to convey. In that case, you better be right about this. You could allow attaching 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 Attachments extension for Magento 2 The module allows uploading files for each product your customers buy. The attaching process is powered by Ajax and does not require reloading the page.

With the module, the user can attach files to order not only on the checkout page but on the order view page as well. All the attachments are protected from public access via generated links. Uploaded files will be shown on Guest Order View and Customer Order View pages. The module allows attaching file links to the email template.

Order Attachments extension works perfectly with default Magento 2 checkout. It is also a part of the Magento 2 FireCheckout extension.