org-mode/doc/pdflayout.sty

% Copyright (C) 2007-2013  Free Software Foundation, Inc.

% This file is part of GNU Emacs.

% GNU Emacs is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.

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% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.

% You should have received a copy of the GNU General Public License
% along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.

% This file defines `\pdflayout':
%  - \pdflayout=(0) is A4 portrait,
%  - \pdflayout=(1) is letter (US) portrait,
%  - \pdflayout=(0l) is A4 landscape.
%  - \pdflayout=(1l) is letter (US) landscape,

\input ifpdf.sty

\ifpdf
  \def\pdflayout=(#1#2){
    \if0#1 % A4
      \pdfpagewidth=21cm
      \pdfpageheight=29.7cm
    \else\if1#1 % Letter
      \pdfpagewidth=8.5in
      \pdfpageheight=11in
      \letterpaper=1
    \fi\fi
    \if l#2 % Landscape
      \edef\oldwidth{\the\pdfpagewidth}
      \pdfpagewidth=\pdfpageheight
      \pdfpageheight=\oldwidth
    \fi
  }
\else
  \def\pdflayout=(#1#2){}
\fi