There's an even easier way to get economist subscription for free, go to the website and subscribe for the least period possible. If I am not mistaken, it's 12 issues. (Don't forget that you have to pick the printed subscription!!) . Get online access to economist.com by going here. Do not renew your subscription when it is due, as you will soon realize that your online access is valid forever!!
Word of caution: I had one year subscription, then decided to not renew it and found out about this sweet magic. Try at your own risk, as after some googling around, I think it has to do with the way how they organize their user database. Funny thing, that they don't have capable IT people over there, :p. Have fun!
If it doesn't work, try the other method here using calibre. Everything is self explanatory, and you'll then be able to transfer the content to any ebook reader, such as kindle.