Preview pdf markup on iPad? I've always loved the functionality Preview.app provides for marking up PDFs.  Using Dropbox allows me to easily see these changes across my mac's, but I'm stumped as to how to not only see, but continue to markup PDFs when I'm using my iPad. 

Is there a native app or setting I'm missing? I've tried using iBooks, but I cannot annotate there on a pdf like I can an ePub. 
If there isn't a way to do this out of the box, does anyone have a favorite third party solution?
As limited as it is, but just for annotations, Adobe Reader for iDevices does support most (if not all) annotation types.

Other PDF viewers support annotations as well, and if you want to have more functionality, particularly when it comes to PDF forms, you might look at PDFExpert by Readdle.