I don't believe that we have provided an all inclusive OMD pdf for quite a few years. With the current release you will find a pdf for each unique assemblies OMD after you install the developer kit at:
<Dev Kit Install Dir>\Diagrams
(example: C:\Program Files\ArcGIS\DeveloperKit10.0\Diagrams)
For 9.x it would be located at:
<ArcGIS Install Dir>\DeveloperKit\Diagrams
(example: C:\Program Files\ArcGIS\DeveloperKit\Diagrams)