A lot of us here at TUAW use Readdle's PDF Expert (US$9.99) to view, annotate, and organize Adobe Portable Document Format (PDF) files. The app has always provided a useful and fast way to mark up PDFs, and there's a new update available that adds some very useful features.
PDF Expert 4.0 now supports the Retina display of the new iPad, a feature that works incredibly well. Readdle went through all of the UI elements of PDF Expert and updat
