Senior Product Designer, Ursula Sadiq, has an article about Project Freewheel collaboration on her In the Pipes blog:
P&ID Markups with [Project] Freewheel
Although the 3D/2D ShareNow Add-in for AutoCAD, Inventor, and Revit installer only locates and installs for vanilla AutoCAD, Ursula includes the steps to manually install for AutoCAD-based applications such as AutoCAD P&ID (Piping and Instrumentation Diagram). Check it out.