%%
%% The LaTeX Companion, 3ed
%%
%% Example A-4-4 on page II-678 in "Special hooks available in the \protect \nxLenv  {document} environment".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3exa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{207.0pt}

%StartShownPreambleCommands
% Assume this to be inside the document
% class, for example, as part of a ``draft''
% option declaration:
\AddToHook{begindocument/end}
          {\begin{center}%
              \fbox{Draft material}%
          \end{center}}

\usepackage{kantlipsum}

%StopShownPreambleCommands

\begin{document}
\kant[1][1]  % the text by the author ...
\end{document}