Welcome, I am a new Kindle owner as well. Since I was unable to change the font size or zoom in on a pdf if I used the drag and drop method I had to find another solution. I download the free software Calibre and use that to convert to mobipocket formet where I can change the text size so i can actually see the PDF.
Calibre is free and can be found at
http://calibre-ebook.com/ and is very, very easy to use.