Creating an accessible web content, whether it is PDF or HTML, can benefit all users, not just those with disabilities. Many accessibility features stem from an approach that requires an understanding of how people use the web. Considering accessibility can also have the effect of making a PDF friendlier to search engines.

Most importantly, a simple and consistent page layout will help users to easkly navigate your PDF, making it simpler for them to undestand and navigate. Creating structure makes pages more accessible to people using assistive technologies such as screen readers. However, a good structure is not enough; you also need to consider the accessibility of your PDF content.

If you are using images or multimedia, some thought must be given to conveying the message contained in that content to a user that cannot see it. Text-based alternatives can be 'read aloud' to people with visual impairments using a screen reader like JAWS. Less obviously, a well code document allows a search engine to index the content of your files more accurately. For example, without them, a search engine is not able to understand the meaning contained within an image or video.

Different content requires different approaches. For instance, providing transcripts of audio will help hearing impaired users and descriptions of video benefit those with sight problems. Similarly any graphs, charts or images can be described using special markup attributes.

Keyboard shortcuts are useful to people with manual dexterity problems who struggle to use a mouse. Access keys provide a means for a user to directly navigate to specific parts of a PDF by pressing the respective keys on the keyboard. Similarly, a "skip keys" feature allows a user to skip past the current page's navigation bar and navigate straight to the content. Otherwise, to access links in the main body, they would be forced to tab through all the navigation links first -- an annoying requirement.

Writing using simple, straightforward language is critical for those who suffer from cognitive difficulties: concentration problems for instance. There are various accessibility techniques that achieve high readability. First, plenty of headings should be provided to give clues about the essence of each section. Also break down the body of the text into manageable chunks. Short paragraphs with plenty of space between them are ideal. General readability can be assessed using the Flesch readability test.

Ensure there is sufficient contrast between the color of the text and its background, reducing strain on the eyes. Also, the words used for any hypertext links should be understandable in their own right, giving an indication of where you are linking to. "Click here", for instance is not very informative but "view our prices" is much more understandable.

Other accessibility features involve some simple programming techniques, such as allowing the user to change the PDF text size. If your design uses strong colors and not the typical black text on a white background, some users may struggle to read it. To solve this, offer the option to change the color of the text and background to something more suitable.

These are just some of the commonly used accessibility features. Designing a PDF is all about balance and it must be understood that not everyone can be accommodated equally. However, by making your WCAG, AODA, PDF Accessibility, Section 508, you are making it available to as many users as possible.