Appending a full version of a document

Question

I have a document written in tex, although it is a shorter version of a larger document. For example, my short document is 10 pages, and once I elaborate on some parts in the shorter document, it will become 15 pages. I would like to create a new document which is essentially 25 pages long, the first 10 pages of which is the short document and the last 15 pages of which is the long version (placed in an appendix). The content of the 15 page part would repeat a lot of content from the first 10 pages.

I have two questions.

1. Is it possible to compile the short version and the long version together in one tex file (i.e., so the content of the entire 25 page document lies in the same tex file)? The only way I know of would involve a lot of work regarding changing label names/references, equations, etc.

2. I guess there is a way to concatenate the short version together with the long version as two separate pdf files (one 10 pages and the other 15 pages), even though I prefer not to do this. Is pdfpages the best way to do this? What if I want the appendix part to begin in the middle of a page at the end of my short document (and not on a new blank page)?

Here is an example. This will result in warnings though, which I want to avoid, and I would have to change the labels individually to fix these warnings (not only are there warnings, but right now both equation references refer to the second equation in the appendix):

\begin{document}

\section{main}

My equation:
\begin{equation}\label{eqn:addition}
1 + 1
\end{equation}
Equation~\ref{eqn:addition}

\appendix

\section{main}

My equation with some elaboration:
\begin{equation}\label{eqn:addition}
1 + 1
\end{equation}
Equation~\ref{eqn:addition} with more elaboration

\end{document}

Answer 1

If I understand the problem, you are worried about the warnings/errors regarding labels.

LaTeX Warning: Label `eqn:addition' multiply defined.

One way to avoid that is to redefine \label and \ref just before your new content with something like:

\let\OrigLabel\label
\let\OrigRef\ref
\renewcommand{\label}[1]{\OrigLabel{NEW##1}}%
\renewcommand{\ref}[1]{\OrigRef{NEW:##1}}%

which automatically changes the any new uses of \label and \ref to refer to the new content. That is any use of \label{foo} and \ref{foo} after the \renewcommands is treated as if you had typed \label{foo-new} and \ref{foo-new}.

Furthermore, with amsmath we also need to redefine \label@in@display as per How to redefine \label command in align environment.

Code:

\documentclass{article}
\usepackage{amsmath}
\usepackage[colorlinks=true]{hyperref}

\makeatletter
\newcommand*{\StartNewContent}{%
    \let\OrigLabel\label%
    \let\OrigRef\ref%
    \renewcommand{\label}[1]{\OrigLabel{NEW##1}}%
    \renewcommand{\ref}[1]{\OrigRef{NEW:##1}}%
    \renewcommand{\label@in@display}[1]{%
        \ifx\df@label\@empty\else
            \@amsmath@err{Multiple \string\label's:
                label '\df@label' will be lost}\@eha
        \fi
        \gdef\df@label{NEW:##1}%
    }%
}
\makeatother


\begin{document}

\section{main}

My equation:
\begin{equation}\label{eqn:addition}
1 + 1
\end{equation}
Equation~\ref{eqn:addition}

\appendix


\section{main}
\StartNewContent

My equation with some elaboration:
\begin{equation}\label{eqn:addition}
1 + 1
\end{equation}
Equation~\ref{eqn:addition} with more elaboration

\end{document}