MuPDF is a modular, actively developed:
lightweight PDF, XPS, and E-book viewer
MuPDF is developed as free software under version 3 of the Affero GNU General Public License.
Go to the mupdf downloads page http://mupdf.com/downloads/ to find the latest version; currently http://mupdf.com/downloads/mupdf-1.10a-source.tar.gz.
Move to a directory where you'd like to build the package from source and grab the source files:
tar -zxvf mupdf-1.10a-source.tar.gz
Enter the working directory and consult the README which recommends installing with the following command:
make prefix=/usr/local install
Cross your fingers and hope that everything worked.