Plesk should have a bandwidth sharing feature that lets website visitors become part of the website's server.
For example, a person has 1 dedicated server with Plesk and the person wants to reduce his bandwidth use. So he goes into Plesk, chooses bandwidth sharing, and this generates a software, person puts this software on his website and visitors download and run it, and when people access the person's website from now on they will be downloading some data from the web server and some data from all the visitors who have downloaded and running the software that makes their internet connections become part of the server. Of course the people who downloaded the software won't be able to see/edit/delete/download/upload any files on the server.
For example, a person has 1 dedicated server with Plesk and the person wants to reduce his bandwidth use. So he goes into Plesk, chooses bandwidth sharing, and this generates a software, person puts this software on his website and visitors download and run it, and when people access the person's website from now on they will be downloading some data from the web server and some data from all the visitors who have downloaded and running the software that makes their internet connections become part of the server. Of course the people who downloaded the software won't be able to see/edit/delete/download/upload any files on the server.