Allow access to files only from my site (like anti-leech)

Hello,

first of all, I am not server administrator, but I have to find solution for this.

I've got a server which serves files. System windows server 2012 with IIS 7+. Then I have website, which is hosted on another machine and another system. I would like to allow requests only from my website call it xxx.tld which is connecting to server through http request (http://IP/file.doc). 

I've already tried to check for HOST, but mobile phones or tables won't send HOST header, so the content is not accessible from mobile devices.

Is there any solution for this?

Thanks for reply.