"The latest iPad app from Readdle, a company famous for its excellent productivity apps for iOS, has perfected PDF annotation and note taking on a touchscreen device."
The difference between this one and PDFPen from Smile on my Mac appears to be that this one actually is a note taking program along with a PDF annotater. Oh, and its about four bucks cheaper at $5.99 USD [affiliate link]. I also think that PDFPen is a bit more polished and has a couple of advantages namely it syncs with the desktop version and has iCloud syncing. But if you just want a standalone PDF program and like to take notes on your iPad, this one would work just fine. If you have used either program, tell us your thoughts!
__________________
iPhone 4, 1.6 GHz Core 2 Duo MacBook Air, Apple TV, 2.66GHz Intel C2D Mac Mini, 1TB TC, Airport Extreme,several iPods and an iPad, 32GB Wi-Fi version. Follow me on Twitter.