Hi!
3D Dimensions/Annotations are not supported in Ray Tracing nor Inventor Studio renders.
There's no good option to achieve this but...
I suggest you use the Visual Style as "Realistic" and activate shadows and reflexion to get a nice image.
Also, i use to insert the image in Powerpoint or an image editor (like Photoshop, Gimp, etc), and create the dimensions manually.
You can request this option at the Inventor Ideas forum and expect the functionality to be implemented in future versions.