Move section out of part

Question

I am using the document class article. Once I place a part in the document, all subsequent sections belong to the part automatically. How can I reset a section such that it does not belong to a part?

The following sample demonstrates what I want to achieve:

\section{Introduction}

\part{Part 1}
\section{Section 1 belonging to part 1}
\section{Section 2 belonging to part 1}

\part{Part 2}
\section{Section 1 belonging to part 2}
\section{Section 2 belonging to part 2}

% should not belong to Part 2
\section{Conclusion}

Answer 1

The \bookmarksetup instruction will lift the final section one level up in the PDF bookmarks; the \addtocontents instruction will leave the same space in the TOC as before parts.

\documentclass{article}
\usepackage{hyperref}
\usepackage{bookmark}
\begin{document}

\tableofcontents

\section{Introduction}

\part{Part 1}
\section{Section 1 belonging to part 1}
\section{Section 2 belonging to part 1}

\part{Part 2}
\section{Section 1 belonging to part 2}
\section{Section 2 belonging to part 2}

\addtocontents{toc}{\protect\addvspace{2.25em plus 1pt}}
\bookmarksetup{startatroot}
\section{Conclusion}
\end{document}

Answer 2

I'm not sure, what you want exactly. You might want the starred form of \section and reset the section-counter:

\documentclass{report}

\begin{document}
\section*{Introduction}

\renewcommand{\thesection}{\arabic{part}.\arabic{section}}
\part{Part 1}
\section{Section 1 belonging to part 1}
\section{Section 2 belonging to part 1}

\setcounter{section}{0}
\part{Part 2}
\section{Section 1 belonging to part 2}
\section{Section 2 belonging to part 2}

% should not belong to Part 2
\section*{Conclusion}
\end{document}

You may want to add a clearpage before the Conclusion section as well.