It is possible to either use the configured main map service of the project or the specific SynExtractService configured for the WebOffice extract server extension.

ArcGIS Server Map Service (extract) - WebOffice category

ArcGIS Server Service capabilities with activated WebOffice extract server extension in ArcCatalog
Note: See WO extract server User Manual 10 R3.pdf for details on the property page attributes of SynExtractService in ArcMap.