http://sourceforge.net/projects/jodconverter/

JODConverter automates conversions between office document formats using OpenOffice.org. Supported formats include OpenDocument, PDF, RTF, Word, Excel, PowerPoint, and Flash. It can be used as a Java library, a command line tool, or a Web application.

usage:

To convert multiple files to a given format specify the format using the
-f (or --output-format) option and then pass the input files as parameters

java -jar lib/jodconverter-cli-2.2.0.jar -f pdf *.odt

source: http://www.artofsolving.com/node/13

    *  DOC to PDF, DOC to ODT, DOC to RTF
    * XLS to PDF, XLS to ODS, XLS to CSV
    * PPT to PDF, PPT to ODP, PPT to SWF
    * ODT to PDF, ODT to DOC, ODT to RTF
    * ODS to PDF, ODS to XLS, ODS to CSV
    * ODP to PDF, ODP to PPT, ODP to SWF