In order to update the text of your PDF document for ADA functionality; begin by opening the PDF with Adobe's Accessibility Feature.
Once opened, you can change and update the text order and update all the tags on each page in Adobe
You can find the full details about Adobe's functionality here:
First you must Enable ADA. To do that:
1. Go to Design Template:
2. Go to
Features:

3. Enable ADA:
Below are the basic steps to access and use the Accessibility Features. Make sure you are in Adobe:
1. Open the Tools pane:
2. Choose the Accessibility Tool:
3. Choose Reading Order:
4. Choose the image to which you want to add the compliance text, right-click, and choose Edit Alternate Text:
5. Type in the image description, then select the OK button to finalize this step:
6. Close the Reading Order window once you are satisfied with text you've entered.
7. After successfully editing the tags to your liking in Adobe, export the file in the following manner:
File->Export To ->Text (Accessibility)