In the past few years, we have covered many WooCommerce plugins that make your store more user-friendly. The Easy Upload Files During Checkout extension is ideal for accepting file attachments during checkout. It lets you control the types of files allowed and make uploads required for orders.
The premium version of this plugin lets you upload multiple files. You can also limit max upload size on the settings page. Want to allow file uploads only for certain types of products? No problem. You can have the plugin upload files to Amazon S3 for maximum security.