Characteristics of Accessible PDF Files-2

Accessible PDFs include, but are not limited to the following characteristics:

Searchable text 

A document that consists of scanned images of text is inherently inaccessible, because the content of the document is a graphic representing the letters on the page, not searchable text.

Assistive technology software cannot read or extract the words in a graphical representation. Furthermore, users cannot select or edit the text, or manipulate the PDF for accessibility. Scanned images of text must be converted into searchable text using optical character recognition (OCR), before addressing accessibility in the document.

Here is an example of a PDF image that does not have searchable text. Download PDF image that does not have searchable text.

Fonts that allow characters to be extracted to text

Fonts in an accessible PDF must contain enough information for Acrobat to correctly extract all of the characters to text, for purposes other than displaying text on the screen. When you read a PDF with a screen reader or the Read Out Loud tool, or when you save as text for a Braille embosser, acrobat extracts characters to Unicode text. This extraction fails if Acrobat cannot determine how to map the font to Unicode characters.

  Interactive and descriptive form-fields are tagged in a logical reading order & no restricted time submission

 

PDF form accessibility is out of the scope of this self-paced course due to its complexity. 

Forms must provide identification, give tips on proper completion, and provide a logical reading order in the form of tags. Form entry should not be timed unless the user can request more time.

 

 

 

 

 

 

Other interactive features: Hyperlinks and navigational aids

Navigational aids in a PDF — links, bookmarks, headings, a table of contents, and a preset tab order for form fields — assist all users in using the document without having to read through the entire document, word by word. Bookmarks are especially useful and can be created from document headings. These features can be accessed using the keyboard without relying on the mouse, allowing users multiple ways to navigate content.

 Document language, title indication, & security

Specifying the document language in a PDF enables some screen readers to switch the current speech synthesizer to the appropriate language, allowing correct pronunciation of content in different languages. Providing a document title allows the user to locate and identify the document.

Security that will not Interfere with Assistive Technology

Some authors of PDFs restrict users from printing, copying, extracting, editing, or adding comments to text. The text of an accessible PDF must be available to a screen reader. Acrobat’s security settings can be set to protect document content while not interfering with a screen reader’s ability to convert the on-screen text to speech or Braille.

 

  Document structure tags & proper reading order

PDFs need correctly structured tags, as screen readers or other assistive technologies determine information, like reading order and interpreting the document, based on the tags panel. 

PDF tags identify the reading order, headings, paragraphs, sections, tables, images, tables, and other page elements.

The tag's structure allows for documents to be resized and reflowed for viewing at larger sizes and on mobile devices.

 

 

 

 

 

 

 

 

 

 

 

  Alternative Text Descriptions for Non-Text Elements

The user of a screen reader cannot understand document features, such as images or interactive form fields, unless they have associated alternative text.

Though link text is available to screen reader users, it is possible to provide more meaningful descriptions via actual text. Alternative text for images and tooltips can aid many users, including those with learning disabilities.

Accessible equivalents for multimedia, including any audio and video elements, must also be present.

 

 

 

 

  Other Accessible Document Characteristics

There are additional characteristics of accessible documents, including:

• No reliance on color or sensory characteristics alone to convey meaning.
• Use of color combinations that provide a sufficient degree of contrast.
• Controls for audio.
• Use of text instead of images of text.
• No use of flashing or blinking elements.
• No focus changes without user initiation.
• Consistent navigation and identification of elements.