There are two ways to make a PDF accessible: remediating it yourself using accessibility tools like CommonLook PDF or have it remediated by professionals.
Making a PDF accessible is an elaborate process; this is why we have created a comprehensive, step-by-step layman’s guide. Our latest white paper, How to Make a PDF Accessible: A Step-by-Step Guide for Beginners, outlines the entire process to get you started on your PDF accessibility journey.