Nowadays, governments and corporations alike are putting an ever-increasing number of accessibility laws in place to ensure that disabled audiences are not put at a disadvantage. How can technical documents best be styled in order to be accessible to low-vision or colour-deficient people while at the same time not causing an inconvenience to the typical reader?
As someone with many friends with varying levels of visual impairment, the most effective tricks are the most obvious. I answer here for printed documentation.
Text should be high in contrast, clear dark black ink on white paper. Recently, too many user manuals seem to be printed in a greyish ink on greyish paper. This affects clarity for many forms of impairment.
Use a clear font / typeface. Similar glyphs, e.g. 0 and O, 1 and l, should be clearly distinguishable if at all possible. There is significant research on fonts for this purpose. Fonts designed for dyslexics, like Dyslexie Font are particularly good.
Use colour sparingly. Coloured text can be harder to read, just like the greyish text I mentioned above. Bear in mind that the most common form of colour-blindness is red-green. These two colours can be confused but are the most commonly used. Use shades of the colours that will be distinguishable by their darkness alone. Even those souls with complete black-white colour-blindness can differentiate the intensity of the colour.
These simple tricks are effective and don't impair the readability for those with perfect eyesight.
I think Sejal and Chenmunka hit a lot of the points that are important when writing for audiences with disabilities. I would add that it's also important to have your content well-tagged semantically. By that, I mean that a screen reading tool needs to know how to interpret the information it's reading. Otherwise it's just a jumble of words and it's difficult to understand the importance of each piece of information or how to navigate through the information to find what you need.
So, you want to have your titles, section titles, tables, figures, and everything else really well-tagged so that information can be conveyed to the end-user and they can understand the relevance of each part of the documentation as it's read to them.
Adobe has some tools for tagging content that can help you achieve this in PDF. HTML tends to have more inherent tagging of content (H1, H2, etc.).
Another option is to source your content in a more structured format, such as XML/DITA. This adds some structure to your content by default and also provides built-in mechanisms for making your content more accessible, such as adding alternative text to images.
Additionally, if you start with structured content, the publishing output is usually separated from the writing process, so once you get your styling right in the publishing plugin, you can ensure that everything you publish will be consistent and accessible.
Webaim.org has quite a few free tools that can check your content for accessibility issues. These two are a couple of my favorites:
Accessibility in writing is a widely discussed issue and there are a number of resources available on this. Vision impaired people generally use screen readers such as JAWs to "read" documentation. So, other than the obvious styling fixes (which may be useful for color blind audience) there are a few more precautions you can take up as a writer,
- Ensure that you don't refer to colors, shapes, and directions in your documentation content and if you do, have an alternative explanation handy.
- All images should have an alternative text that is used by screen readers to explain the image.
- The diagrams shouldn't be the sole way to explain your content, but should be treated more as an added bonus to your text. So you must have relevant textual description explaining everything in the graphic.
- Tables should have accompanying descriptions.
- PDFs are usually not accessible, HTML is.
- Use OAG tool to check your html page accessibility.