The iPad and iPhone have always been great for reading PDFs, and lately Apple has added more tools for annotating them. Yet, there are third-party alternatives that are so exceptionally good that you need them whenever you're working with PDFs.
As much as we fail to give Apple's free Preview app enough respect, it is true that there are PDF editing jobs it can't do. Yet there are many third-party apps that will let you do the most remarkable changes to any PDF you have.
Addressing a feature lacking native support from iOS, developer Readdle has announced a new drag-and-drop feature for its own apps, including PDF Expert, Spark and Scanner Pro, that works in the iPad's split-screen multitasking view.