In order to make your PDF accessibility friendly, you must follow some standards as you would do when producing accessibility friendly HTML documents.
A good starting point for that are the accessibility guidelines provided by mozilla.org.
Also check out the Web Accessibility Evaluation Tools List from W3C to verify your HTML.
Feel free to get in touch with us if you are having trouble with your PDF, we are happy to help.
Add meta tag to identify your document to support PDF/UA standard.
By default typeset.sh does not add the XMP identify which identifies your PDF as UA friendly, even when it is. This is because it requires manual effort from the author of the document and to validate the PDF to make sure everything is fine. By adding the following meta tag to your your head, typeset.sh will add the proper XMP identifier.
<meta name="WCAG" content="2.1">