IPAD3 or KINDLE FIRE HD for my personal pdf files and descent skipe.?

[Skywalker]

The Kindle Fire HDX would provide you more portability, is lesser in weight and the cheaper one making it best bang for your bucks. You can easily read PDF's on it and those PDF's generally dont have any kind of issues where you cant read on one device and read on other. They work in a universal way.

Comparison and a list of pros and cons - Kindle Fire HDX 8.9" vs iPad 3:

http://compare-e-readers.com/KindleHdx9IPad3

And as far as the Skype is concerned, it works good on both devices too, you'll get a good picture quality and definitely a better experience of calls. So Kindle Fire HDX would be the better option as you get what you want in cheaper, whereas iPad 3 can be a bit expensive option and you get an Apple device.

Hope this helped!