How to require user to pay first using paypal before being able to download a file in drupal?

How to require user to pay first using paypal before being able to
download a file in drupal?

I am trying to learn more about Drupal 7 and I am quite stuck in
implementing this functionality.
What I am trying to do is to create some node having some files in it and
if a visitor will click on the download link for the file, if he is not
logged in or if he/she does not have an account yet he will be asked to
pay first in paypal. Once the payment is successful he/she will
automatically receive an email having the login details.
As for now, I am using the Paypal API module which provides some help but
the problem is that is restricts the visitor in seeing the entire content
of the node where I only want to limit the user to download the file if it
isn't paid yet.
I also have tried to search on some modules and ubercart could be an
option or drupal commerce but I feel like they are too massive for this
little functionality for me site.
Is there a simple and efficient solution for what I am trying to accomplish?