Adding Tags to a PDF
("Less Easy" Method)
PDF document does not contain Tags, but contains text content (searchable PDF)
PDF created using Distiller, etc.
Sample Workflow in Adobe Acrobat:
Use "Add Tags to Document" function
(under Advanced > Accessibility on menu bar)
Add additional descriptions to images and check for logical reading order of content
P.S. Don't make a mistake there's no undo!