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PDF was invented for publishers. The publishing industry has used PDF since the format was first released in 1993. At the time, the combination of high-fidelity print and on-screen appearance with reliable portability between operating systems and around the world was a major innovation for the distribution of final-form documents.

Due to this history, publishers think they understand what PDF is all about. Today, they have some frustrations. The rise of smartphones and Kindles using a variety of small screens has triggered the need for an electronic content model that doesn’t have much use for a fixed layout.

So, some ask, if we increasingly use phones and Kindles to read, maybe we don’t really need a technology that’s rooted in the concept of a hardcopy page anymore? If we have EPUB, do we still need PDF?!?

The Latest Challenger

EPUB logo and Wikipedia entry.It’s not the first time that some have suggested that PDF is old, over the hill and ready for retirement. Over the years other formats have stepped up as big-picture challenges to the orthodoxy of easy, fast and functional PDF. Nothing happened – all vanished beneath the PDF behemoth. Who needed Microsoft’s XPS when there’s PDF? It’s a fair question, and there wasn’t a good answer.

Now comes EPUB, and most recently, EPUB 3. This newest version of EPUB offers a “fixed layout” model and the ability to deliver fully self-contained content, two of PDF’s core differentiators. EPUB has other great features – it’s based on XML and styling may be completely customized for different screens and needs via HTML 5 and CSS conventions. For some, it naturally follows that if EPUB’s base technology (XML) is super-duper and if EPUB meets a couple of key PDF features then it should “win”.

They would be wrong. PDF is a totality, a package of concepts, complete with attendant seeming-limitations that are – in reality – just as valuable as the format’s features. PDF mimics paper. PDF works well in workflows that have (or must allow for) hardcopy. Also like paper, PDF offers a sense of authenticity, a moment in time. Similar to paper (and unlike a web-page) it’s possible to be formal, to mark up with annotations, to redact, to add digital signatures, to treat each page as a physical entity. PDF pages are digital representations of physical reality, readily transmutable (by printer and scanner) between those two realms for a million and one purposes.

Consider a typical academic setting. A professor wants to create a body of materials for her students, including chapters from her own book, selected pages from other sources, screen-shots, web-pages and so on. It’s important to be able to quickly refer others to specific material in the collection, be able to replace pages, work offline, highlight sections, and so on. It should be accessible to all students, including those with disabilities. Above all, it needs to be easy.

You can do (most) of that with paper, and of course, all of it with PDF. To convince the professor to go with something else, you’re going to need to show at least that much capability. While the same outcome is, in principle, more or less achievable with EPUB 3, the resulting file wouldn’t enjoy any of EPUBs advantages.

PDF is General Purpose, it’s an Easy Button for Authors

The PDF format was designed to meet the needs of publishers twenty years ago, but those definitions have expanded ever so slightly since 1993! Today, everyone’s a “publisher” because everyone can (and does) make PDF.

The list of uses for PDF goes far, far beyond the distribution of polished books, magazines, journals, textbooks and the like – these are now a tiny minority of PDF files. Since PDF does such a great job of acting like paper in the digital domain, it turned out that PDF was the natural format for documents ranging from legal briefs to application forms to construction drawings to bank statements to receipts.

EPUB (even EPUB 3) doesn’t even contemplate such uses, much less best PDF in accommodating them.

EPUB is Plastic, PDF is Concrete

EPUB 3 Overview screenshotRead the EPUB 3 Overview (note the careful styling – eerily similar to a W3C specification) and it’s plain – EPUB is about meeting the needs of publishers and consumers of considered, carefully produced works. Fundamental to EPUB is the ability to reflow smartly on smaller screens. It’s a fine subset of the world of electronic documents and their uses, but it’s only one relatively modest subset.

If PDF isn’t used for delivery of a given iBook, that’s fine – there are other great technologies for that purpose such as EPUB. If business people can’t readily pull together a collection of arbitrary pages into a single document in a consistent, reliable and functional fashion, then Houston, we have a problem.

With broad acceptance among a variety of publishers, there’s no doubt that EPUB is “for real” – it should be. Mobile devices make special demands on content, and publishers with products to sell can and should take advantage of that. PDF can also perform well in a mobile setting, but that’s a different question (with [[what-is-pdfua PDF/UA]] as one of the answers).

While the web began and continued to evolve as a riot of crazy-quilt technologies, PDF was, is and will remain a rock of stability. PDF technology might be boring to web-heads, but it still gets the job done billions of times each day all over the earth, and it will continue to do so. EPUB won’t replace PDF any faster than plastic will replace concrete.

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