For Interactive PDF, Not All Readers Are Equal
While EPUB and the Adobe Digital Publishing Suite draw a lot of attention, the most popular kind of digital publishing produced in Adobe InDesign is interactive PDF. Interactive PDF has been around for several years and can be produced by most recent versions of InDesign.
It's popular because it's easy to produce, and it maintains the appearance of a print document. And PDFs can be viewed on virtually any platform?Macintosh, Windows, Unix, as well as tablets and smartphones. Sounds perfect doesn't it?
Unfortunately, on user forums you often see messages like these:
I created a document in InDesign CS4 that includes videos ( MOV). When I export to PDF, and the PDF opens on my desktop it shows the videos, as soon as I email it or transfer it to a different computer the videos no longer show up.
Or this one:
I have been sent some PDF forms to fill in, and I did so in Preview. All looks OK, except two of the fields can't be typed in.... Preview doesn't appear to be fully compatible with PDF forms created with PC's.
In the old days, Adobe controlled the PDF format and most people viewed PDF in Adobe Reader for Mac and Windows. However, PDF is now an ISO standard, and there are dozens of different PDF readers on different platforms. They vary widely is now much of the PDF specification they support, and messages like these reflect that fact.
Here's an example: I have written before that the best format in which to include video in digital publications is H.264-encoded. I placed a video file in InDesign CS5.5 and exported as an interactive PDF. In Adobe Acrobat or Reader, the video plays fine.
The first user quoted above viewed their video (which happened to be a MOV file but would see the same thing with H.264) in Apple's Preview. When I viewed my video in Apple Preview, I saw nothing at all:
Then I transferred the PDF to my iPad and viewed it in several PDF readers. You would expect that the Adobe Reader for mobile devices would have no problem, but all it shows is the poster image. The movie file (in any format) doesn't play:
Finally, I viewed it in several other PDF readers (Apple iBooks, GoodReader, PDF Expert, and ezPDF Reader). Only ezPDF Reader and PDF Expert* could actually play an embedded video file:
What Works and What Doesn't
Here's an overview of some other common features in interactive PDF files and how they work. I couldn't test all applications or apps, or all platforms. My testing was on my Macintosh and my iPad (iOS operating system).
Internal Links: Links created in InDesign to other text or objects in the same PDF worked well in Apple Preview and most iOS PDF readers. But links don't work in Adobe Reader for iOS.
URL Links: URL links created in InDesign work in Apple Preview. All iOS PDF readers I tested except Adobe Reader for iOS support them.
Navigation Buttons: Buttons like Go to Next Page or Go to Previous Page work in Apple Preview, Good Reader (iOS) and PDF Expert (iOS) but not the other apps. But no other application or app I found supports other kinds of buttons (like Show/Hide).
Embedded Bookmarks: Bookmarks created in InDesign or Adobe Acrobat appear in Apple Preview. They work in all iOS readers I tested (including Adobe Reader for iOS). However, they may appear with different names, like Outlines or Table of Contents. Most readers also allow the creation of Bookmarks but these are not cross-application compatible and only work in the same reader.
Annotations/Markup: Annotations created in Adobe Acrobat appear or partially appear in Apple Preview, Good Reader (iOS), ezPDF Reader (iOS), and PDF Expert. They can be created in these applications but are generally not cross-application compatible. And not all the annotation types created by Adobe Reader/Acrobat are supported.
Interactive Forms: As the second user comment above pointed out, there are problems with interactive forms created in Adobe Acrobat and opened in Apple Preview. iOS ezPDF Reader and PDF Expert also support opening forms and filling them in. I didn't have time to test whether they corrupt Acrobat forms but I would be very wary.
For interactive PDF files which will be viewed on a computer (Mac or Windows), I think you should strongly suggest to your readers they they view your file in Adobe Acrobat or the free Adobe Reader. As I mentioned in the video posting, if you embed H.264-encoded video, they need to use at least Acrobat or Reader 9 or later in order to view them.
For interactive PDF files which are to be viewed on a tablet device, you need to reduce your expectations that interactivity will be able to be viewed by every viewer. I'd keep things simple, and don't make your presentation depend on showing all the interactivity. But Adobe Reader for iOS is very disappointing, and I cannot recommend it. GoodReader ($4.99), ezPDF Reader ($2.99) and PDF Expert ($9.99) are well rated and support many more features.
App developers on the iPad have added many new features to their PDF viewers in the past year, and I expect that strong competition between them will improve viewing of interactive PDF files in the future.
*PDF Expert added 4/2/12