Your attached PDFs needn’t be inert. With Bookends you can search and mark up PDFs, adding your own notes, highlights (with notes if you like), comments, and underlining.
So how is that any more useful than markup done in any of dozens of other PDF annotating applications? Because PDF notes in Bookends are directly tied to the note stream, and appear in editable notecards.
See all your PDF’s notes and highlighted text at a glance, click on a notecard to be taken right to the note in the PDF, and edit them in the PDF or edit notes in the Bookends notecard (they’ll be written back to the PDF).
And because Bookends uses an open standard for PDF markup, its annotations can be shared with apps such as Preview, Adobe Reader, Bookends On Tap (of course), and many more.