I am certainly no expert on creating accessible PDFs, but here's what we figured out today. A PDF we scanned resulted in two columns of text that were being read across the columns, rather than going down one column and then moving on to the next, as it should. For instance, it was reading the text below as "At age three Katherine Schneider discovered An expert living on disability, she has she was blind" rather than "At age three Katherine Schneider discovered she was blind."
My amazing student used his Google skills to learn that first we needed to add the Accessibility panel in the right side of Acrobat Pro by going to View, then Tools, then selecting Accessibility, as in the screenshot below.
Then under Accessibility, "TouchUp Reading Order" allows you to select text in the order you want it to be read. There was an image, so I added alternate text describing it. I will send it to Katherine in the hopes she can now read it with a screen reader and update this post if necessary.