Documentation for DevForce 2009 and early DevForce 2010 was maintained in PDF form as the DevForce Developers Guide.
Please take heed: the Developers Guide has been retired in favor of the online "DevForce Resource Center" (DRC) Documentation which you are reading now. Today we only maintain DevForce 2010 documentation online here in the DRC.
Only the DRC Documentation is authoritative for DevForce 2010; the Developers Guide is deprecated and will become progressively less accurate and less relevant for DevForce 2010 developers.
DevForce 2009 developers may wish to consult the Developers Guide; DevForce 2009 is feature-frozen and the guide should be reasonably accurate.
If you decide to download the Developers Guide, please read it with a healthy dose of salt nearby.