Question: how to scale the canvas to the known real world dimension of objects?

Probably a n00b question … yes, I’m a n00b ;-)

I’ve imported a visio doc of an office space layout that needs remodeled. I know the visio at some point had a true real world scale, but that scale is not correct in omnigraffle.

If know the real world dimensions of a few walls in the layout, how can I set the canvas so it’s correctly scaled?

The canvas units inspector is discussed towards the end of this article:
https://support.omnigroup.com/documentation/omnigraffle/mac/7.1/en/working-with-the-inspectors/

Change your ruler units and scale in the Canvas: Units inspector, so that the dimensions of a wall you know are correct (in the Object:Geometry inspector).