Academic journal article Information Technology and Libraries

Are PDF Documents Accessible?

Academic journal article Information Technology and Libraries

Are PDF Documents Accessible?

Article excerpt

Adobe PDF is one of the most widely used formats in scientific communications and in administrative documents. In its latest versions it has incorporated structural tags and improvements that increase its level of accessibility. This article reviews the concept of accessibility in the reading of digital documents and evaluates the accessibility of PDF according to the most widely established standards.

In a world in which an increasing amount of information is circulating in digital format, document accessibility is becoming a major concern. Many countries have adopted legislative measures concerning digital accessibility (see, for example, the Web Accessibility Initiative at www.w3.org/WAI/Policy) and the guru of the Web, Jakob Nielsen, has included it in several columns (Nielsen 1996, 1999) and reports (Coyne and Nielsen 2001a, 2001b, 2001c; Schade and Neilsen 2002).

Improving document accessibility for disabled persons, including the elderly, offers good business opportunities for IT firms. For example, Sun has introduced strict accessibility guidelines in its Java programming language, and Microsoft has incorporated an increasing number of assistive technologies in its operating system. For its part, Adobe came out clearly in favor of accessibility in the latest updates of its flagship format, PDF, and its free Reader program (Adobe 2005).

The efforts of these and many other companies are necessary if persons with disabilities are to be able to use products as well as persons without disabilities. In an effect similar to that of the cascade of interactions that takes place in the search for information in a digital library (Bates 2002), the accessibility of a digital product is contextual and depends on many layers: the product itself, the application used to operate it, the support of the operating system, and the additional assistive technologies used to transform the content (Henry 2007). For example, an HTML document is considered to be accessible if it complies with the Web Content Accessibility Guidelines (WCAG 1.0) (W3C 1999, W3C 2006), but it is only usable if the browser with which it is consulted provides the options of accessibility (e.g., by allowing users to modify the associated style sheet), if the user has the necessary assistive technologies--screen magnifiers, screen readers, alternate pointing devices, etc.--to use the information and functionality contained in the document, and if all these tools interact correctly with each other. This article focuses on the accessibility of the PDF due to its importance in the world of digital publishing. Though we do not have global statistics on its use, a Google search specifying PDF as the format returns 236 million documents, whereas none of the other recoverable formats reaches 50 million documents (Postscript 10 million, Microsoft Word 37 million, Microsoft Excel 14 million, Microsoft PowerPoint 14 million). (The search was performed on April 14, 2007, with the arguments filetype:pdf, etc. Values were rounded off to the nearest million.) It should be remembered that PDF is the main format used for digital publishing of electronic journals and for a great variety of administrative documents, including e-government communications. Furthermore, the subformat PDF/A for archiving is the preferred format for digital preservation in many large libraries, including the Library of Congress, which recommends it for textual documents in which the appearance is more relevant than the structure (Library of Congress 2005). Finally, according to a study by Forrester Research in 2005, PDF/A and XML will be the dominant formats in document archiving in 2008 (Markham 2005). If our digital memory is going to be in PDF, we must ensure that it is accessible to all persons.

So far, the many studies that have been carried out on the accessibility of digital information have considered mainly the accessibility of Web content in HTML. Digital documents in a broad sense have never been evaluated from an accessibility viewpoint, and the only user studies carried out on them have dealt with usability--without paying particular attention to special capacities (see Dillon 2004)--or user preferences with regard to articles in electronic format (Tenopir 2003). …

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