Accessibility is the process of enabling access to information and services to people with disabilities such as blindness, low-vision, or physical impairments.
The World Wide Web Consortium (W3C) has published strategies, guidelines, and resources to make the Web accessible to people with disabilities. For information on their Web Accessibility Initiative, see http://www.w3.org/WAI/.
In Australia, the Disability Discrimination Act 1992 prohibits direct and indirect discrimination on the grounds of disability. The Human Rights and Equal Opportunity Commission has published information about how organisations and individuals can make their websites and publications accessible in order to comply with the law. For more information, see http://www.humanrights.gov.au/disability_rights
Note: PDF accessibility is a large topic, and a full discussion of it is beyond the scope of this article. In this article, we will briefly examine modifying reading order.
Alpha Computer Consultants run a full day course on creating accessible PDFs—visit www.alphacc.com.au for more details.
Because many organisations publish PDF documents on their websites, it is important to make them accessible.
But accessible PDFs benefit all users. For instance, the tag structure that enables a screen reader to properly read a PDF out loud to a blind person also enables a mobile device to correctly reflow and display the PDF document on a small screen, such as a hand-held device like a Pocket PC. Also, setting the tab order of a PDF form will help all users, not just those with physical impairments, complete the form more easily.
Searchable text: a document with a scanned image of text is inaccessible because its content not searchable text. Users cannot read, select or edit the text. Use Acrobat's optical character recognition (OCR) features to convert the scanned image of text to searchable text.
Alternative text descriptions: images and form fields cannot be read by a screen reader unless they have alternative text.
Fonts that are accessible to screen readers: the fonts in an accessible PDF must have enough information to be read with a screen reader or Acrobat's Read Out Loud tool.
Reading order and document structure tags: in order for a screen reader to read a document's text and present it in a way that makes sense, the document must be structured using tags. Tags define the reading order and identify headings, paragraphs, sections, tables, and other page elements.
Interactive form fields: form fields must be interactive, i.e. a user must be able to enter values into the form fields.
Navigational aids: navigational aids such as links, bookmarks, headings, and a table of contents assist all users in finding the information they seek without having to read through the entire document. Bookmarks are particularly useful and can be created from document headings.
Security that does not interfere with screen readers: ensure that the document's security settings do not prevent a screen reader's ability to convert on-screen text to speech.
A PDF document's tags indicate its structure: which text is a heading, which text is a subheading, which text is normal body text, etc. The structure of the tags represents the organisational structure of the document, indicating the precise reading order and thus improving navigation.
The document structure tags are used by screen reader devices to determine the correct reading order of text and to give alternative text descriptions for images and other content.
These same document structure tags are also used to reflowing a PDF document for viewing on the small screen of a mobile device or hand-held computer.
In an untagged document, no organisational structure exists, and Acrobat must guess a structure. This is unreliable and results in text being read in the wrong order or even not read at all.
The TouchUp Reading Order tool lets you view and correct the reading order of a tagged PDF document. When you select it, a dialogue box opens that lets you display highlighted areas showing the order of the page's content.
The highlighted regions are numbered, and the number indicates the region's placement in the page's reading order. You can use the TouchUp Reading Order tool to assign content type to parts of a PDF.