During export, you can include the content of another file. For example, to include your .emacs file, you could use:
#+INCLUDE: "~/.emacs" src emacs-lisp
The optional second and third parameter are the markup (i.e., ‘example’ or ‘src’), and, if the markup is ‘src’, the language for formatting the contents. The markup is optional, if it is not given, the text will be assumed to be in Org mode format and will be processed normally. File-links will be interpreted as well:
#+INCLUDE: "./otherfile.org::#my_custom_id" :only-contents t
C-c ' will visit the included file.