template.tex

% Reference: https://tex.stackexchange.com/questions/8827/preparing-cheat-sheets/8915

% Package imports.
\documentclass[10pt,landscape]{article}
\usepackage{multicol}
\usepackage{calc}
\usepackage{ifthen}
\usepackage[landscape, a4paper]{geometry}
\usepackage{amsmath,amsthm,amsfonts,amssymb}
\usepackage{color,graphicx,overpic}
\usepackage{hyperref}

% Sets page margins.
\geometry{top=.2in,left=.2in,right=.2in,bottom=.2in}

% Turns off header and footer.
\pagestyle{empty}

% Redefine section commands to use less space and have smaller text.
% (Can change font size if `\tiny` is too small.
% See http://www.sascha-frank.com/latex-font-size.html as a reference.)
\makeatletter
\renewcommand{\section}{\@startsection{section}{1}{0mm}%
                                {-0.5ex plus -.5ex minus -.2ex}%
                                {-0.5\baselineskip}%
                                {\normalfont\tiny\bfseries}}
\renewcommand{\subsection}{\@startsection{subsection}{2}{0mm}%
                                {-0.5ex plus -.5ex minus -.2ex}%
                                {-0.5\baselineskip}%
                                {\normalfont\tiny\bfseries}}
\renewcommand{\subsubsection}{\@startsection{subsubsection}{3}{0mm}%
                                {-0.5ex plus -.5ex minus -.2ex}%
                                {-0.5\baselineskip}%
                                {\normalfont\tiny\bfseries}}
\renewcommand{\paragraph}{\@startsection{paragraph}{4}{0mm}%
                                {-0.5ex plus -.5ex minus -.2ex}%
                                {-0.5\baselineskip}%
                                {\normalfont\tiny\bfseries}}
\makeatother

% No section numbers.
\setcounter{secnumdepth}{0}

% Minimal paragraph indenting and spacing.
\setlength{\parindent}{0pt}
\setlength{\parskip}{0pt plus 0.5ex}

% Canonical "init" statement.
\begin{document}

% Don't start new paragraphs if you don't need to.
\raggedright

% Font size.
\tiny

% Specifying number of columns.
% Asterisk "*" here to force the left-most column to fill first, then the next, ect.
% (Otherwise, all columns would fill down "equally".
\begin{multicols*}{4}

% Can play around with these as desired.
\setlength{\columnseprule}{0.25pt}
\setlength{\premulticols}{0.25pt}
\setlength{\postmulticols}{0.25pt}
\setlength{\multicolsep}{0.25pt}
\setlength{\columnsep}{0.25pt}

% This is the "magic" pandoc variable. (This is where your Rmarkdown document is inserted.)
$body$

% `\end` statements to match the `\begin`s.
\end{multicols*}

\end{document}