seppdflatex
Build a large LaTeX book with separate linked chapters
... chapter files using zr-ref and xr packages from CTAN. But you have to write the correct LaTeX source. The script seppdflatex does the compilation and formatting of Table of Contents and such-like and separates out the chapters as standalone PDF files. The script uses the free software pdftk and pdfsam-console, as well as a bunch of handy CPAN modules, which you will need to install first.