These instructions use Word 2013 but the information is applicable for earlier versions of Word as well. You’ll need to use a PC to export the document or add accessibility directly to your PDF document.
Important: If you are using Word on a Mac, unfortunately there is no equivalent PDF export function that will preserve accessibility features. ACM publications are read (and reviewed) by many people therefore, making your paper accessible will help to promote the equal participation of people with disabilities in science and engineering.
This page gives step-by-step instructions for adding basic accessibility information to a Word document on a PC, then exporting it to a PDF document intended for ACM.