How to limit access to files in a specific directory for non admins/users

I have a form that uploads files along with other information. When I export the data, it outputs the directory location of the file. (i.e. https://www.domain.com/wp-content/uploads/form/my_document.pdf)

This is available to view for anyone with the link. How can I make it so that nobody, UNLESS they are logged-in as an admin, will be able to see anything in say the “forms” directory?

Thanks in advance