How can I tell LaTeX to only make pagebreaks on new sections?

Question

I'm working on a document where it's important that sections are in the same page.

How can I tell LaTeX to only make a page break (if necessary) when I write a new \section without having to manually add \newpages manually?

Answer 1

Macro \section can be redefined to add a \newpage or \clearpage. The latter also forces pending float object to be placed.

% Save the old meaning of \section in \OrgSection
\newcommand*{\OrgSection}{}%
\let\OrgSection\section
% Redefine \section to add \clearpage at the beginning
\renewcommand*{\section}{%
  \clearpage
  \OrgSection
}

Answer 2

With some arrangements, it could be done with a minipage environment whenever the section does not fill more than one page. In other case the text fill the bottom margin without page breaks as in the last section of the MWE (see below).

However, I think that a general rule of thumb is suggest to LaTeX where to break the page, through a \pagebreak[3] (or some less than 3) just before of each section, and where do not break, setting high values in \clubpenalty and \windowpenalty, but let to LaTeX find the better place to break the pages. Then, if the really final result is not satisfactory at some point, you always can use the brute force (a \pagebreak[4], or a \newpage or \clearpage if there are floats, as mention Heiko Oberdiek) where (and only where) really it is needed.

\documentclass{article}
\usepackage{lipsum} % dummy text


\makeatletter
\renewcommand{\section}{
~\par\@startsection
{section}%                   % the name
{1}%                         % the level
{0mm}%                       % the indent
{2\baselineskip}%            % the before skip
{1\baselineskip}%          % the after skip
{\Large\bfseries}} % the style
\makeatother

\begin{document}

\section{Lore ipsum}
\lipsum[1]

\noindent\begin{minipage}{\textwidth}
\setlength{\parindent}{2em}
\section{Lore ipsum}
\lipsum[2-5]
\end{minipage}

\noindent\begin{minipage}{\textwidth}
\setlength{\parindent}{2em}
\section{Lore ipsum}
\lipsum[6]
\end{minipage}

\noindent\begin{minipage}{\textwidth}
\setlength{\parindent}{2em}
\section{Lore ipsum}
\lipsum[7]
\end{minipage}

% Ooops .... too long for a **mini** page
\noindent\begin{minipage}{\textwidth}
\setlength{\parindent}{2em}
\section{Lore ipsum}
\lipsum[8-15]
\end{minipage}

\end{document}