I love Goodreader. Its a great app to read PDFs. Supports PDF of almost any size that I drop into the application. It also support Text files. Common pictures formats like jpeg, png, bmp etc can also be viewed It also has a great slideshow viewer. Even audio/video format files like mp3, aiff, mp4 are supported. File transfer to the mobile phone are supported via US and wifi which makes it easy to use. All this for a cheap price of $4.99 on the iTunes store.