How to include a document into another document?

Question

I have two documents A and B. Both of them are separate documents. But document A also has to include document B.

Now if I use \include{B} i get the following error:

! LaTeX Error: Can be used only in preamble.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.1 \documentclass
                  [11pt]{article}
? 

So how can I force to include document B with the "style" and "template" of document A?

Answer 1

Cut the content (the part between \begin{document}...\end{document} of B.tex into a new file B-content.tex.

Change B.tex to be:

\documentclass{...}
% your preamble here
\begin{document}
\include{B-content}
\end{document}

Then put \include{B-content} into A.tex.

Answer 2

You can use the standalone, docmute or subfiles package to make LaTeX ignore the second preamble.

Simply load the standalone package in the main file and \input or \include the document. This is a good way if the to-be-included documents just holds a picture which should also be compiled standalone. In this case having main files for every picture file would be annoying.

% A.tex
\documentclass{article}
\usepackage{standalone}
% your preamble here
\begin{document}
% ...
\input{B-content}% or \include
% ...
\end{document}

% B.tex (for normal text)
\documentclass{article}
% your preamble here
\begin{document}
% your B content here
\end{document}

or if B should hold some diagram only (note the different class):

% B.tex
\documentclass{standalone}
% your preamble here
\begin{document}
% your diagram code here
\end{document}

Answer 3

As far as I know, include simply inserts the text wherever it is used. So you can't have a preamble in document B. At a quick glance, I would create a wrapper document C and use \include{B} in both after editing B so that it only contains your desired output text

Answer 4

You can try using the combine class but be warned this is not what LaTeX is designed for!

An alternative that I haven't tried is to use the newclude package and write

\includedoc{fileB.tex}

This latter approach assumes that all of the packages, etc., you need are loaded by the first file.