STL format contains mesh data that can usually be be only viewed but not edited. You will need to download the Free Mesh Enabler tool from Autodesk Lab (or maybe also some CAD sites) which allows for conversion of the mesh features to Inventor Base features. The resulting Base features can then be used for further operations including drawings and measurements.
There seems to also exist a special STL plugin for Autodesk Inventor, which can be used to import STL files to Inventor..Open STL file Open IPT file
Autodesk Inventor is modeling application used to create 3D digital prototypes
A 2D and 3D CAD construction software