Traditional documents contain several items that can present accessibility barriers, including images, charts and tables. Almost all of what is presented in a document is visual, and therefore can present difficulties for individuals with vision disabilities. Though there are document formats that can contain sound, it is beyond the scope of this module. Keep in mind that spoken audio needs to be transcribed.
A key element for Adobe Reader is the ability to expose elements to screen readers. A screen reader is a piece of software that someone uses to read content via a synthesized voice. Previous versions of Adobe Reader were not able to expose elements to screen readers and therefore made the document inaccessible to these readers.
Adobe Acrobat has the capability to scan in documents
and save them as PDF files. The problem with this is that Adobe Acrobat
saves the document as an image, instead of translating the document it
scanned into text. This problem can be addressed through the Capture
Agent Pack
,
which has the ability to recognize words from the scanned document, and
save the document as text instead of an image, greatly opening up the
document's accessibility. This process is beyond the scope of this module,
but if interested, visit the Capture Agent Pack from Adobe for additional
information.
Though several of the previous accessibility issues have been automated, the main issue now lies on the shoulders of the document designer, who must have a good idea of how the document is to be structured. This is discussed below in more detail. The general idea is that not only should you expose the content of the document, but meta information such as its layout and reading order as well.
If you are familiar with the generation of web content,
you probably know that HTML is a markup language which simply defines
the structure of the document. HTML is meta-data that surrounds the actual
content, and defines how that content is to be presented or interpreted.
For example, the <H1> tag in HTML
defines text as being extremely important, while a tag such as <H2>
is less important, with <H3> being
less important than <H2>. This defines
the relationship among the elements in the document. Structuring a document
is also called 'tagging' a document. This is an important idea that will
be discussed later in the module.
Structure is extremely important to screen readers, because it defines how the document is to be read to a user. People without vision disabilities can pick up on clues to determine the importance of a piece of text by looking at the font size, its color, the font family, or its location. These attributes are irrelevant to a screen reader. Things such as tables or multi-column documents can be ambiguous. But what is important to the screen reader is the structure of the document; in other words, the screen reader is interested in the relationship between the content in the document, not in its appearance.
Adobe Acrobat covers up many of the issues associated with structure, provided the original document was authored with some structure in mind. Adobe Acrobat actually creates a tree hierarchy during the conversion process for its content (see Image 12). The tree shows the relationship between all of the elements in the document. More specifically, the tree represents the reading order of the document. To see more information on how to structure documents, see Lab: Structure in PDF.
According to Adobe, a tagged PDF file:
(Source: Accessibility
FAQs: What makes tagged Adobe PDF files more accessible? )
Another important concept in accessibility is providing alternative text for images. Just as structuring your document provides key information as to the layout of the document, alternative text is a short description of the image. An example of this can be found by moving your mouse over any image on this page. You may, depending on your browser settings, see the text equivalents pop up after a short period of time. It is only necessary to provide an overview of what the image is if it provides important contextual information. For example, if a document contained a picture of stars in space, that may be relevant if the document is talking about astronomy topics. This would be less important if the image was used as a background.
If you are unfamiliar with this topic, visit Alternative Text in PDF.
Another issue that is important is defining the language of the document. Office 2000, for example, can automatically detect the language of most documents through its 'Proofing Tools'. If the document language is not specified, it will be brought to your attention when using the accessibility checker. It is also possible to define the language of a document in Adobe Acrobat.
Many PDF files were created with old applications, so many PDF files are not tagged. Remember, tagged PDF files define structural and relational information about the content. While older PDF files were able to define structure, they did so in a way that was inaccessible.
To 'retrofit' older PDF files such as those made with Acrobat 4, Adobe created the 'Make Accessible Plug-in'; this plug-in has the capability of automatically analyzing the structure of a document. The plug-in adds the appropriate tags, creating the tree hierarchy previously discussed.
Unfortunately, this plug-in will not work for documents that were scanned in, simply because a scanned image is not the same as text. Thus, Adobe has developed the Capture Pack that has the ability to read the text from a scanned document. This technology is not free.
Most older PDF files were scanned and retrofitting them
is important. For this process, you will need Acrobat 5.0 and you will
probably need to purchase the Capture Pack software. You will also need
to download the free Make
Accessible Plug-in.
The process of Retrofitting
Older PDF Files is discussed in more detail within the Lab: Structure
in PDF.
Forms allow users to fill out information electronically,
including common components such as textfields and radio buttons. The
form can then be submitted electronically. Many government institutions
are now in the process of converting their current paper-based system
to an electronic system. Adobe has created tools to help with large batch
processing of these forms called the Capture
Pack from the Adobe website
The Capture Pack includes a tool named the 'Forms Access' tool.
Because Adobe Acrobat is an excellent tool for creating forms, you will more than likely run into a time that you will need to make form elements accessible. Forms elements can present accessibility barriers, much in the same way images can. Form elements, by default, can not be seen by screen readers, thus making the form unusable for people with certain disabilities.
When working with forms, its necessary to insert the form element into the tag hierarchy, and to give it a valid name. Doing so exposes the name of the element to the screen reader, allowing it to be read correctly. It is important to remember to structure elements in a document correctly and that providing a name for elements is not enough.
Because working with forms is so common, please review the Lab: Forms in PDF. The lab starts with a common PDF form. It then walks you through how to add form elements, give appropriate names to them, and insert them into the tag hierarchy.
The next page will present information on the structure and reading order within PDF.
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