When re-creating an item using the Reading Order Pane, you are basically redefining an element on the page with a given tag-type. This procedure should normally be used for one-offs and not the entire pdf document.
If you find the entire pdf document is not tagged, you should go back to the source document (MS Word or the like) where the pdf was generated from and when printing/exporting to pdf, ensure the option "Document structure tags for accessibility" is checked.
This procedure assumes you have the pdf open in Adobe Acrobat and have selected the "Accessibility" tool within it.
- From the right-hand list of options, choose "Reading Order". This will open up the Reading Order Pane.
- Window-select the items in the document that need to be created/re-created.
- Select the option-type from the buttons in the Reading Order Pane, such as Text/Paragraph, Figure (images and graphics), Table, Heading 1-6, etc.
The selected items are now converted to the new option-type and should now be shown wrapped in a grey box with a number in the upper-left corner.