I am working on a custom WordPress theme, and i am little stuck in one situation, the client wants that when the user buy subscription on his WordPress site, then the user can download documents, (the users are downloading documents its done). Now the problem is that, the download should be limited as per plan choice, for example:- if a user buys $100 subscription pack then..user can click on download button.. for only 50 times. and if he buys $200 subscription pack then..user can click on download button.. for only 100 times. (*note:- the download button is available on every post so , every time when user click on any post download Resume button, the count should be -1. until he reaches to 0 and disabled download button )
I don’t have any clue how to do this, is there any specific key idea behind this or any WordPress plugin to do this thing.

Here below is the image to get an idea of the concept ;
view Image here