Is it possible to input a file while lowering every section it has by 1 level?

Assume that I want to add a part of a paper I've wrote into a different document.

Inside the new document, the part of the paper should be only a section, so every section of the paper would become a subsection, and every subsection should become a subsubsection.

For example, assume I have the document:

\documentclass{article}
\begin{document}
\section{Doc A}
\input{docA}
\section{Conclusions}
Very good.
\end{document}


While docA.tex has:

\section{Hello}
This should actually be a subsection.
\subsection{World}
And that one is a subsubsction.


When compiling the document I get:

How do I make every section/subsection in the input file go one level lower, such that the Hello would become Subsection 1.1, and World will then be Subsubsection 1.1.1 (i.e., there should only be 2 sections in the outer doc)?

Obviously, this can be done by modifying docA, but I prefer not to change it if possible.

• Have a look at package coseuol. – Johannes_B Feb 8 '16 at 11:49
• @Johannes_B - I can't seem to find the package. Do you have a link or something to it? (is it spelled correctly?). Thanks ! – R B Feb 8 '16 at 11:56
• No, typo. ctan.org/pkg/coseoul – Johannes_B Feb 8 '16 at 12:03
• Thanks @Johannes_B. Unfortunately, it doesn't seem to work for me, as it requires to modify the way docA works (replace \section and \subsection with level-downs). I want to use the input document without changing it. – R B Feb 8 '16 at 12:18

\documentclass{article}
\begin{document}
\section{Doc A}
{
\let\section\subsection
\let\subsection\subsubsection
\input{docA}
}
\section{Conclusions}
Very good.
\end{document}

• Took me about 45 min to find this answer after digging through all the standard \input \include noise. Thanks David! – FizxMike Jul 23 '17 at 20:06