The author writes: "Did I mention that both Word and LibreOffice generate tagged PDFs?" But then the simple solution is this: Convert your LaTeX to Word or Li

The author writes: "Did I mention that both Word and LibreOffice generate tagged PDFs?" But then the simple solution is this: Convert your LaTeX to Word or LibreOffice. Then generate the PDF. Absurdly the easiest way to convert LaTeX to Word/LibreOffice is by creating a PDF first (https://tex.stackexchange.com/questions/111886/how-to-convert-a-scientific-manuscript-from-latex-to-word-using-pandoc https://tex.stackexchange.com/questions/111886/how-to-conver...), import that into Word/LibreOffice and then create your PDF/A from that.