Service Pack for PDMWorks Workgroup 2008?

Hi,
We are currently running SW2008 SP3.1 with PDM Workgroup SP0.0 Icannot find any way to upgrade PDM to the latest service pack.

Is service pack 3.1 for PDMWorks workgroup available (I can onlyfind it for the enterprise version)?

And if so, how do I upgrade?

Any info much appreciatedSolidworksWorkgroup Pdm