Generating Well Tagged PDF from LaTeX

% Using the \DocumentMetadata command results in a tagged and accessible PDF file.
% Use ‘pdfversion’ and ‘pdfstandard’ keys to select the output file type.
\DocumentMetadata{
  lang        = en,
  pdfversion  = 2.0,  % or 1.7 if desired pdfstandard = ua-1
  pdfstandard = ua-2, % or ua-1 if pdfversion = 1.7
  pdfstandard = a-4,  % or a-4f (see below)
  testphase   = latest
}

% The next declaration results in a tagged PDF with MathML included via structure elements (tags).
% Remove this declaration to generate a tagged PDF with MathML Associated Files, as the use
% of this feature requires the PDF file to declare conformance with PDF/A-4f rather than PDF/A-4.
% LaTeX will automatically switch to declare PDF/A-4f if Associated Files are used when the
% document declares pdfstandard = a-4.
\tagpdfsetup{math/mathml/structelem, math/mathml/AF=false, math/tex/AF=false, math/mathml/sources=}

\documentclass{article}
% Using Unicode math fonts improves the tagging of math.
\usepackage{unicode-math}

% Classic LaTeX document markup from here.
\begin{document}

\section{A small example}

Some inline mathematics involving $x\in\symbb{R}$.

A list of items
\begin{enumerate}
\item a first item;
\item a second item;
\item a third item.
\end{enumerate}

Display math
\[
c=\sqrt{a^2+b^2}
\]

\end{document}

\DocumentMetadata{
  lang        = en,
  pdfversion  = 2.0,
  pdfstandard = ua-2,
  pdfstandard = a-4f,
  testphase   = latest
}

% Remove the next declaration to generate MathML Associated Files rather than Structure Elements
% The file would then need to declare PDF/A-4f rather than PDF/A-4 conformance.
\tagpdfsetup{math/mathml/structelem, math/mathml/AF=false, math/tex/AF=false, math/mathml/sources=}

\documentclass[a4paper,twocolumn]{article}

\usepackage{unicode-math}
\usepackage{graphicx}

\begin{document}

\title{A Larger Example}
\date{2024-12-17}
\author{The \LaTeX\ Team}

\pagestyle{headings}

\maketitle

\begin{abstract}
  An example document showing automatic tagging of typical structures
  found in a \LaTeX\ document, including titles, sections, lists,
  citations lists and mathematics. A two column layout is used, the
  tagging enables the reading order to correctly follow the flow of
  text through the columns.
\end{abstract}

\tableofcontents

\section{Introduction}

This document shows a typical two-column document incorporating tables, figures and mathematics.

Apart from two commands at the start to enable tagging, and a small
amount of additional markup to give alternative texts for graphics
inclusion, and to specify the heading rows of tables%
\footnote{The current tagging markup for tables is temporary and a new interface
for tagging tables will be developed.}. The document
just uses standard \LaTeX\ markup that would be used in any \LaTeX\
document since the 1980's.

\section{Document structures}

\subsection{Mathematics}

Let $p$ be a prime, then
\[n^p=n \mod p\]

An aligned set of equations:
\begin{align}
  f(x)&=\sin x + \cos y \\
  g(x)&=2\cos x - 3\sin y
\end{align}

Matrices.
\[
\begin{pmatrix}1&2\\3&4\end{pmatrix}
\begin{pmatrix}1&1\\0&1\end{pmatrix}
=
\begin{pmatrix}1&3\\3&7\end{pmatrix}
\]

\subsection{Lists}
Lists often occur in documents
\begin{itemize}
\item They may be unordered bullet lists
\item Or may be numbered lists.
  \begin{enumerate}
  \item lists may also be nested in an outer list
  \item \label{item-a}items within such a list may be referenced.
  \end{enumerate}
\end{itemize}
Here we reference item~\ref{item-a}.

\subsection{Figures and Tables}

Small images may be shown inline
\includegraphics[height=1em,alt=small skull in a diamond]{ghsystem_skull.jpg}
and small tables may be shown within the paragraph:
\begin{center}
\tagpdfsetup{table/header-rows={1,2}}
\begin{tabular}{lr}
\multicolumn{2}{c}{Example}\\
Name&Value\\
This& 11 \\
That & 2
\end{tabular}
\end{center}

Larger figures are usually placed in a \emph{float} to be positioned at a suitable
place to help with column and page breaking.
\begin{figure}
  \centering
  \includegraphics[alt=example image A,width=.9\linewidth]{example-image-a}
  \caption{Larger image set as a \emph{float}}
\end{figure}

\subsection{Citations}
It is also possible to cite works from a bib\TeX\ database, here we
cite \cite{article-full} and \cite{inbook-full} from the
\texttt{xampl.bib} sample file distributed with bib\TeX.

\bibliographystyle{plain}
\bibliography{xampl}

\end{document}