Development work required on Magento 1 Website

We operate a Magento Ecommerce site (Magento ver. 1.9.3.7). We currently have the functionality built in that enables a customer to upload a PDF version of a Purchase Order and for this to populate the basket automatically.

The Purchase Order template is provided by the customer and is configured specifically for that customer's account.

I need a fixed cost for configuring future Purchase Order templates so that when we offer a customer this option, they send us their standard Purchase Order as a PDF and we add the function.