ModelSpace->PaperSpace ViewPort transformation

[Anonymous]

Here is my question:
I have 3D model in Modelspace and a couple of paperspaces with viewports. I would like to darw some dimensioning stuff on those paperspaces over the model, but do not know coordinates transformation rule.
What am I missing? It sounds like a quite straightforward thing.

Thanks,
Valeriy Raygorodetskyy