For iBooks and it's free. If you install it and are unable to find the app, restart your iPad and then it will show up. I had this problem and after doing some searches in google it seems to be a common problem but works great after that.
Here is the tutorial for How to Convert PDF to Epub for iPad.
Simply a click the PDF file has been converted to Epub. Then you can sync the Epub files to your iDevice via itunes.
Hope it can do you a favor.