You can use the 3D Text tool to put text on faces in the model. Keep in mind that it can add lots of geometry and bloat your model file. Or you can use the Text tool to add labels that have leaders anchored to faces.
When I tried that I was able to open my model file but only in read-only mode. I went to my File Explorer and clicked on it to open and was able to edit the model and save it.
If you want to draw accurate arcs/circles, tangents, intersections etc etc then you might try my 'True Tangents' - the tools in the script do various tasks, including giving you the true intersection cpoint[s] between a selected arc/circle and a line which you can then use for a replacement arc/circle and edge that will have proper intersections with the line...
See here http://forums.sketchucation.com/viewtopic.php?p=160780#p160780