Information given by colour
Someone suffering from colour blindness won’t be able to see the difference and a blind person will not get the information. It is possible that the information is not sufficiently understandable for those suffering from a cognitive disability.
Text size and contrast
Information is unreadable if the contrast is too low. To highlight an element, the use of bold in addition to colour is of great help to blind persons.
Absence of alternative text
Images that include text are informative images. If they do not provide alternative text then blind persons will not be able to access the information.
Active elements which have been deactivated
Elements such as links, table of contents, bookmarks, etc. are considered as complex elements. The hyperlinks will not be notified: making them active will ease navigation for the blind. Moreover, active elements ease the navigation for persons with reduced mobility: they can easily access the web pages they wish to browse through keyboard navigation.
Specific editorial content
Long URLs can hinder understanding during transcription carried out by a screen reader. It is also preferable to rewrite acronyms using a tag to facilitate understanding as these elements are transcribed by assistive technologies. Some users can be confused by the presence of URLs in the body of the document.
In order to establish the foundations required during the creation of PDF files, one must understand how blind or visually impaired persons navigate through a PDF file. To navigate, these persons use assistive technologies such as screen readers, braille displays and/or keyboards.
In the accessibility preferences of Adobe Reader, they can choose among various PDF document-reading modes :
- Only Read the Currently Visible Pages
- For Large Documents, Only Read the Currently Visible Pages
- Read The Entire Document At Once
Selecting the “Only Read the Currently Visible Pages” option prevents screen readers from being overloaded, and prevents the full loading of open documents.
They generally start off by going to the table of contents that regroups all the titles of the document. To read the content, these persons can use the up and down arrows to move from one line to another throughout the document, regardless of the reading mode selected. When they reach elements such as lists, titles, hyperlinks, tables, form fields: the screen reader will indicate their nature. There are specific keyboard shortcuts to navigate through these elements. They may differ depending on the screen reader used (NVDA or JAWS).
People suffering from a mobility disability also use special keyboards or the standard keyboard to navigate through the document.
A blind or visually impaired person can use a “screen reader” to vocalize what is appearing on the screen. There are two main screen readers for desktop computers using Windows: JAWS and NVDA. In addition to reading the elements out loud present on the screen, these screen readers offer a wide range of keyboard shortcuts to navigate through the content with greater ease. Although not free, JAWS is the most popular and most commonly used because it is more advanced in terms of functionality and assistance.
For Apple computers, it is the “VoiceOver” reader that is used. However, this software is not compatible for PDF browsing.
There are also some screen readers for mobile devices. “VoiceOver” is used on Iphones/ Ipads, “Talkback” on Android devices (Smartphones, tablets) and “Narrator” on Windows phones.