\pagestyle{fancy}


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\fancyhead[L]{\slshape \nouppercase{\leftmark}}

\fancyfoot[]{}
\fancyfoot[RE, LO]{Documentation ChemPID}
\fancyfoot[RO, LE]{Page~\thepage}

\renewcommand{\footrulewidth}{.5pt}

%\fancyhead[RE,RO]{\thepage}
%\fancyhead[RE,LO]{Guides and tutorials}
%\fancyfoot[CE,CO]{\leftmark}



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% marginparsep = 0pt,
% bottom = 2.2cm, 
% left = 3.4 cm, 
% top = 2.7 cm,
% right = 2.5cm,
% }
% \setlength{\evensidemargin}{1.0cm}
% \setlength{\oddsidemargin}{1.0cm}
\setlength{\textwidth}{420pt}