Hi,
When you use the Ajax File type custom fields, you can see that when you upload a file in it, if there is already a file in the field, the new file replace the old one in the file. And the system only saves the last one in the database when linking it with the product in the cart/order.
So there is no way to display links to all the files uploaded for that product. The data isn't there in the database. It's just that the files aren't cleaned when the customer replaces the file by another one.
If you want several files, you need to have several custom fields.