OpenOffice for Linux OS is included in phpdocx pro + plugin and corporate versiones. But you can use any version of OpenOffice.
To run openoffice in headless mode execute this command:
$ lib/openoffice/program/soffice -headless -accept="socket,host=127.0.0.1,port=8100;urp;" -nofirststartwizard
lib/openoffice/program/soffice is the path to OpenOffice executable.
Regards.