WebOffice 10 R3 provides high quality printing in various different resolutions. As map caches are available in one resolution (screen resolution, 96dpi) only, printing on cached map services is not supported.
Anyway it is possible to configure a specific print service, which must be based exactly on the same map document as the cached map service. This ArcGIS Server service is used for generating low and high resolution plots.
Tip: Whenever you use map caches, provide an additional service based on the exactly same map document like the map cache service and use this service for printing. Another option is the use of dynamic printing (see chapter Dynamic printing setup for details).