Is there an easy way to do this? I’m doing some screen captures for print, and I would like to add 2D annotations to the Perspective viewport (for labels and instructions), perpendicular to the camera. Anything?
Set CPlane to View and then Text.
Thank you!
Or make details in Layouts and annotate with Text there.
How do I reset the Perspective view back to its default orientation when I’m done? Sorry for the questions - not something I’ve done before in Rhino. 
Cplane > Undo to go back to the previously used Cplane in that viewport.
Or Cplane > world in this case.
And to get back to the CPlane you used to create the annotation, you can select the object and then CPlane -> Object.
You can save your custom CPlanes too.
Use Dimension > Leader. In Settings, set Text to “Horizontal to View”
The text orientation will always be parrallel to the viewpoint.
Max.
In Rhino for OSX? How?
Opps, nevermind. Didn’t notice it was for Mac.