Heading Tags – A heading is text in a PDF that indicates a document title or section in a PDF. If you imagine a PDF is a book, then the headings are like the title and chapters in a PDF. H1 headings would be the main title of the PDF. H2 headings would be like the chapters in a book. If the book is a textbook, H3 – H6 are like the sub-headings within chapters. Try to be consistent with your sub headings.
To tag text as a heading, open your PDF and go to Advanced > Accessibility >Touch-Up Reading Order Panel (or click on the icon in the toolbar if you’ve placed it there)
Draw a rectangle around text that you want to label as a level 1 heading and click Heading 1.
If the “show page content order” is checked on the Touch Up-Reading Order Panel the text you just selected should now be highlighted in gray with a number on the left-hand side.
To tag as heading level 2 or 3, click Heading 2 or Heading 3, respectively.
To tag as heading level 4 – 6, tag as 1 -3, then change the 3 to a 4, 5 or 6 in the tag panel much the same way as you would rename a file on your computer.