GoodReader is a very popular offline-capable PDF reader for the iPad. Here we take an indepth look at the app in this review.
Here is the high-level summary: this app is mediocre to poor. While there is nothing seriously wrong with it, it suffers from a low framerate, glitchy next/previous page interaction, and a lack of annotation features. Bottom line: it could be much better.
GoodReader will let you do the basics. You can download PDF files from a website using the built-in browser. Then you can view the files. Here you can see the browser being used to download a PDF file.
Once you get the file downloaded, you can view it. Here is where most of our problems occurred when testing the system. Basically, the viewer is a bit slow and creaky. The framerate is below 8 FPS, which means that there is visible lag when you go from one page to the next, or when you pinch to zoom. So it's ugly but usable.
The other major problem with reading documents is that there is no way to annotate them. Want to highlight a passage? Want to draw on it with your finger? Can't be done. This is a fairly serious omission from any reader, in particular this one. So if you want to do any kind of serious reading and annotating on this app, forget it.