Add instructions to build documentation

docs-source/usersguide/library.rst

@@ -695,6 +695,63 @@ of the time.  These tests will say so in the error message:
 
 Congratulations! You successfully have built and installed OpenMM from source.
 
+Building the Documentation (Optional)
+*************************************
+
+The documentation that you're currently reading, as well as the developer guide and API
+documentation can be built through CMake as well.
+
+User Guide and Developer Guide
+==============================
+
+Generating the user guide and developer guide requires the following dependencies
+
+* Sphinx (http://sphinx-doc.org/)
+
+* sphinxcontrib-bibtex (https://pypi.python.org/pypi/sphinxcontrib-bibtex)
+
+These dependencies may not be available in your system package manager, but should
+be installable through Python's ``pip`` package manager. ::
+
+   pip install sphinx sphinxcontrib-bibtex
+
+The developer and user guides can be built either as HTML or a PDFs. Building the
+PDF version will also require a functional LaTeX installation.
+
+To build the HTML version of the documentation, type: ::
+
+  make sphinxhtml
+
+To build the PDF version of the documentation, type: ::
+
+  make sphinxpdf
+
+
+Python and C++ API Documentation
+================================
+
+The following dependencies are required to build the Python and C++ API documentation.
+
+* Sphinx (http://sphinx-doc.org/)
+
+* sphinxcontrib-lunrsearch (https://pypi.python.org/pypi/sphinxcontrib-lunrsearch)
+
+* sphinxcontrib-autodoc_doxygen (https://pypi.python.org/pypi/sphinxcontrib-autodoc_doxygen)
+
+
+These dependencies may not be available in your system package manager, but should
+be installable through Python's ``pip`` package manager. ::
+
+   pip install sphinx sphinxcontrib-lunrsearch sphinxcontrib-autodoc_doxygen
+
+To build the C++ API documentation, type: ::
+
+  make C++ApiDocs
+
+To build the Python API documentation, type: ::
+
+  make PythonApiDocs
+
 
 .. _openmm-tutorials:
 
@@ -3642,4 +3699,3 @@ The equations of motion can be integrated with two different methods:
    temperature, while using a much lower temperature for their relative internal
    motion.  In practice, this produces dipole moments very close to those from the
    SCF solution while being much faster to compute.
-