Everyone's needs are different so you should do your best to make your presentations accessible to as many users as possible. The key to making your presentation accessible is to have a well designed source file to begin with, and know your audience.
By following the pointers in Slide design and layout and using templates your presentation should be an accessible source of information which can be provided in alternative formats depending on the needs of your audience.
For example, you may have partially sighted users requiring a large print version or the text contents of your presentation may need to be reproduced in braille.
What alternative formats might I be asked for?
This of course depends entirely on a user's needs and to some extent what accessibility software they are using. Depending on the software and version you have there will be a number of different formats you can save your presentation in which may well be sufficient in most cases. For further information on formats read by blind and partially sighted people, see Accessible formats.
Web pages
Most presentation software can save directly to web pages. Providing the presentation has been properly designed screen reader users will be able to navigate your slides via the various headings and subheading levels. Some users may prefer this method of accessing your presentation.
However, the HTML exported from presentation software may not comply with W3C web accessibility guidelines.
Word processor
Your presentation software may have the facility to export directly to a word processor. Typically, an outline can be saved which will have accessible headings and subheading levels to enable navigation through the text contained in the slides. From an accessibility point of view the ability to save the text outline of your presentation to a word processor means that the structure is maintained which facilitates conversion to other formats such as large print. If you have followed the suggestions given in Slide design and layout conversion to large print should be a straightforward process. Depending on the circumstances it may also be beneficial to add text descriptions of any graphics or multimedia elements used.
Audio
Direct conversion to audio formats is now perfectly possible directly from text files of your presentations. At its simplest a basic audio recording in a format such as MP3 can be created using a synthetic speech conversion program. However, properly structured source files can also be converted into formats such as DAISY which allows effective navigation through the various heading levels.
Conversion to audio may require additional descriptions of graphics and multimedia elements to be added to the text source file before conversion.
Open Document Format
Open Document Format (ODF) enables your slides to be accessed on any presentation software which supports ODF. This can be useful if, for example, a user only has a free version of presentation software and your original was created on a proprietary office application.
Braille
Unless you have access to specialist production facilities you will need to have braille produced externally. RNIB offer specialist braille production facilities around the country as do a number of other organisations.
Expecting the unexpected
If any members of your audience are unable to access your presentation for any reason it is always good practice to be able to offer an alternative format after the event. Of course this process is facilitated by having a well designed source file to begin with.
Further information on accessibility for presentation software can be found on the Slide design and layout, Projected presentations, Multimedia in presentations, Transitions and effects, and Producing handouts pages.