What you are after is basically how a Torrent works, parallel part downloads, a standard download link wont work this way. As far as I am aware there is no way to do this without using a torrent like network and a local client. What you can do is have a striped network.
So say you have 2 servers, each holding the same files in the same url path on the same domain, you can use a DNS proxy/roundrobin that basically sends half of the visitors to one server and half to the other when the browser asks for what server the domain goes to.
Here is the digital ocean community link to how to set this up.
With this you will be able to take advantage of both or more servers under load basically allowing you to serve 2x the amount of data at a time then one server, just with a little DNS round robin.
In this article, we will see how to exploit some of the truly excellent and unique possibilities offered by DigitalOcean's global cloud server / data-centre infrastructure to have a geographically-distributed, highly-available application set-up for minimal downtime (and thus dataloss) by managing DNS responses.