Uploading text does is resembles to add an extra note on the cart page?
If it's so then, Shopify by default gives an option called cart notes which you need to enable it from the Shopify backend customize section.
So, the customers will get an option to add the notes on the cart page and then this will be carried to the checkout and then to orders.
kindly let me know if the above is helpful to you or else I can assist you further if you need any changes.
If you want to create a form on the product page then you can use, UI-element-generator
Refer to the above link, this will help you in creating form and can integrate it on the product page.
If you want me to help you in doing the integration