\documentclass{article}
\usepackage{pdflscape}
\usepackage{tikzpagenodes}
\usepackage{lipsum}

\newcommand{\showboxes}{%
\begin{tikzpicture}[remember picture,overlay]
    \draw [red] (current page text area.south west) rectangle
        (current page text area.north east);
    \draw [green] (current page header area.south west) rectangle
        (current page header area.north east);
    \draw [blue] (current page footer area.south west) rectangle
        (current page footer area.north east);
    \draw [black] (current page marginpar area.south west) rectangle
        (current page marginpar area.north east);
\end{tikzpicture}
}

\begin{document}
\section{Portrait Section}
\showboxes{}
\lipsum[4]
\begin{landscape}
\showboxes{}
\section{Landscape Section}
\lipsum[4]
\end{landscape}
\end{document}