Supporting Documents are documents you want speakers/presenters to upload when they submit their abstract. You can enable up to 5 Supporting Documents in the Presentation Portal. For example, a Biography, or an image.
An Additional Document is a document you want the speakers/presenters to upload after they have submitted their abstract. You can enable up to 3 Additional Documents in the Presentation Portal
Additional Documents also give you the ability to only allow papers to be uploaded that have a particular Paper Status and/or between particular dates. A good example of this would be a Final Paper, which you would only want the Accepted Speakers to upload after a particular date.
For more on the topic of Abstract & Presenter management, search "Abstracts" in our Education Resources section.