Publishers with back-catalogs of print-based content are looking for convenient ways to publish their content onto the growing digital platforms. Often times, the digital format they have comfortable with has been the PDF. However, when producing content in the form of eBooks or digital magazines, there are a lot of things that people have to take into account that aren't as simple as exporting a PDF.
Page and Screen Size
PDF was developed for a specific output in mind: print. It has a fixed page size. While this worked for print, in the digital age your "page" is the computer screen. With tablets, smartphones, laptops, etc., there is no standardization of a screen size. You may have a 4:3 ratio on an iPad, but you may have a 16:10 screen size on a Motorola Xoom tablet, or 16:9 on a computer screen. What's more, the physical size of these devices plays a massive role in legibility. It is important for content to be able to adapt to these different devices. Because PDFs are fixed size, this means something that may be intended for one device may be cropped or scaled on another device, which is far from ideal reading experience.
Design for Print Isn't Design for Digital
When you look at print magazines or books, much of the design was based on a variety of factors including economics and production limitations. The size of body type may have been chosen to optimize the amount of content that will fit on a finite amount of page space or a cost limitation of color or substrates. In addition, print products are designed as "one size fits all" because there is no personalization to the reader. These limitations don't apply to digital.
On platforms such as eBooks, text can be resized, reflowed, and repaginated to adapt to the size of of the device and the ability to read certain type sizes. Digital publishing platforms like Adobe Digital Publishing Suite encourages users to create custom layouts for device size and orientations. Someone who is 20 may have an easier time reading small print on a device as opposed to someone perhaps middle-aged. Users of digital devices have become accustomed to their devices personalizing content to their needs. Simply creating a PDF that people may need to pinch to zoom in doesn't give an ideal user experience to your readership, and if you are producing publications that have competition, consumers will opt for the more intuitive experience.
Over the years, Adobe has extended PDF to be able to have interactive elements such as hyperlinks, videos, and even animation. The issues with this are often these interactive elements are dependent on Adobe Reader and Adobe Flash to read these animations. While mobile platforms like Apple iPad and Android are able to natively read PDFs, they often do not natively read the proprietary extensions Adobe has made to the PDF platform. What's more, because Adobe has chosen to abandon Flash for mobile, the viability of interactive PDFs within the growing mobile market becomes questionable.
PDF is a dead-end format. What I mean by this is that the nature of the format mimics what it was intended for: print. Once ink hits the page, the code behind it that created it becomes irrelevant because the content was not intended to move from the printed page to another system, print is the end product.
Many of the platforms that are used in digital publishing today are based on technologies like HTML in order to allow the maximum flexibility between different platforms. Storing content in such a universal way also gives the maximum flexibility for future platforms. As digital publishing is rapidly changing as is the nature of the digital space, locking content into a single dead-end format like PDF only restricts your business opportunities moving forward.
Building a Foundation
When first examining the digital publishing, large companies rush to market based on the current print products that they offer. Because digital publishing is rapidly changing, it is a better investment to create a foundational platform that your digital offerings can grow from, rather than having to constantly patch new "hacks" to your current print workflow.
In the past, publishing has been controlled and powered by larger organizations because of the high initial investments for print. Now, smaller companies that have more flexibility are able to take risks on newer platforms and have the opportunity to develop their organizations in an adaptable way. If large organizations do not do this than they risk forever following behind the industry, rather than defining it.