% set up LaTeX parameters for A4 paper (21 x 29.7 cm).
% allow .5in extra margins, split evenly for one-sided, .5in - 0in two-sided.
\makeatletter{}

% pick up point size of current font
\newlength{\mainsize}
\setlength{\mainsize}{1\@ptsize pt}
\setlength{\topskip}{\mainsize}	% plain has 10pt
\setlength{\maxdepth}{.4\mainsize}	% plain has 4pt
\setlength{\@maxdepth}{\maxdepth}	% this has to be set as well

% A4 paper width = 21cm
\setlength{\textwidth}{21 true cm}		% A4 paper width
\addtolength{\textwidth}{-2 true in}		% allow for printer margins
\addtolength{\textwidth}{-.5 true in}		% extra margins
\setlength{\marginparsep}{10pt}			% 10pt from text
\setlength{\marginparwidth}{1.25 true in}	% margin width
\addtolength{\marginparwidth}{-.25in}		% not too close to edge
\addtolength{\marginparwidth}{-\marginparsep}	% or to text
\setlength{\oddsidemargin}{.25 true in}
\setlength{\evensidemargin}{.25 true in}

% set headers and footers proportional to font size
\setlength{\headheight}{\mainsize}	% height of heading
\setlength{\headsep}{2\mainsize}	% space between heading and text
\setlength{\topmargin}{0cm}		% space at top
\setlength{\footheight}{\mainsize}	% height of footing
\setlength{\footskip}{2.5\mainsize}	% space between footing and text

% compute space left for text
\setlength{\textheight}{29.7 true cm}		% A4 paper length
\addtolength{\textheight}{-6.5\mainsize}	% headers and footers
\addtolength{\textheight}{-2 true in}		% fixed margins top and bottom

\makeatother{}