Many apps can display PDFs on an iPad; that capability is built into iOS. But only a few of them can handle annotations—such as the notes, highlighting, and other elements that you use to comment on the underlying text. Preview, PDFpen, Acrobat Professional, and other Mac programs let you add such markup. The question is how well annotations work on the iPad.
I tried half a dozen iPad apps that claimed to let you annotate PDFs in one way or another. First I used Preview to add a series of annotations (including shapes, overlaid text, a note, a URL link, highlighting, underlining, and strikethrough) to a PDF on my Mac. I then checked to see how well those annotations appeared in the various apps on my iPad. Next, on a fresh document, I added the kinds of annotations available in each of the six iPad apps, exported them back to my Mac, and opened them in Preview to find out how well they survived.
Half of the annotation apps I tried failed those tests. For example, neither LifeForms nor PDF Assistant was able to display any of the annotations I’d added in Preview; SmileyDocs displayed only an added link. None of the annotations I added in PDF Assistant showed up in Preview, and I was unable to export my annotated document to iTunes. (E-mail worked.) Annotations I added in LifeForms and then e-mailed showed up correctly, but exporting to iTunes didn’t work. SmileyDocs doesn’t even claim to be able to save its annotations outside the app.
I had better luck with three other iPad apps. iAnnotate PDF showed all annotations added in Preview except for shapes and overlaid text. In the app itself, I was able to add shapes, freehand drawings, highlights, notes, underlines, and strikethroughs, and all appeared correctly in Preview.
PDF Highlighter showed (and missed) the same annotations from Preview as iAnnotate PDF. Although the annotations I added in the app came through on my Mac, the choices that it offered were few: only highlights, underline, and strikethrough, but no shapes or notes.
GoodReader for iPad ( ) was the only app to faithfully display every annotation from Preview I threw at it. Likewise, nearly all the annotations I added in GoodReader made it back to Preview.
So only two apps—GoodReader and iAnnotate—were able to support most annotations in both directions. The two differ in their ability to get PDFs on and off your iPad. GoodReader can accept documents from a dizzying array of sources, including iTunes, Dropbox, MobileMe iDisk, and Google Docs; it will also open documents sent from other iOS apps. If you use iTunes, then you can effectively edit the document in place—no importing or exporting is required (although GoodReader does ask whether you want to annotate the original or a copy). Using other import-export methods, such as the cloud or e-mail, is a multistep process: You import the document into GoodReader, edit it, and then copy or move it to the destination.
iAnnotate accepts files via iTunes syncing or other iOS apps but doesn’t connect directly to cloud storage. To retrieve a file from iTunes, you must export the edited version (which takes three taps); you can also e-mail the file. When exporting a file, you can choose to save it as an annotated PDF (the annotations can then be edited in another program), as a “flattened” PDF (with all the annotations converted to plain text or graphics), or as the original, unannotated version.
Both apps have their strong points, but I favor GoodReader for its fidelity when displaying annotations and its flexibility in getting documents in and out. My preferred workflow is to drag a PDF to my Dropbox or iDisk; then, in GoodReader, I tap Connect To Servers -> servername and tap the document name; then I tap the document again in the My Documents list and add my annotations. To make an annotation, I tap and hold a place in the file, and then tap Note, Highlight, Markup, or Draw from the pop-over menu that appears; additional controls appear as needed. When I’m done, I again tap Connect To Servers -> servername, and then I tap Upload, select the document, and tap Upload 1 Item.
Senior Contributor Joe Kissell is the senior editor of TidBits and the author of the e-book Take Control of Working with Your iPad (TidBits Publishing, 2010).