Nice looking application, it is always good to have PDF reader with you on your phone.
To my surprise, there are not so many good PDF readers around.
I have installed your application, I got some errors while viewing my PDF's (
java.lang.OutOfMemoryError: bitmap size exceeds VM budget, several times
Force Close). I can download a LogCat for you, if you are unable to reproduce this error yourself.
My comments are:
1. Nice graphics in file browser,
2. Icons in the document could be bigger/more clear,
3. For next/previous page you could use fling gesture - more convenient than small icons on the bottom,
4. There is one feature that I would give you a million dollars for... (just kidding

). A would like to have bookmarks in the PDF viewer! If I read a technical document, very often I need to mark several pages and then easily switch between them. Please, please, please, give me bookmarks

5. Are you familiar with PDF Viewer from HTC Corporation? It is included in the original firmware with HTC Sense for HTC Magic device, at least in my region. This program has a very interesting mode of document displaying. It is called reflow view. In this mode, text is "flowing" on screen, you can zoom in the text, fonts are getting bigger, but lines are wrapped and are always as long as width of your screen. It is very comfortable to read such texts, you could consider to implement this in your program.
Keep working on it and good luck.