Of course, these days, there's the Send to Kindle app for PC or Mac - the book/document goes into your Archives and can be downloaded to whichever Kindle you'd like.
Downloads & directions here:
Mac version:
http://www.amazon.com/gp/feature.html/?docId=1000778781
PC version:
http://www.amazon.com/gp/feature.html/?docId=1000719931