Both the .obj and .step files are quite common 3D models, so there should be no problem to find some CAD/3D modeling software capable of converting one to another or vice versa. Plenty of choices for this conversion are listed below.
Convert 3D object graphics to ISO-10303 STEP product data.
We found 12 software records in the database related to .obj to .step file format conversion.
Microsoft Windows software - convert obj to step on Windows
A 2D and 3D CAD construction software
Convert from obj file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned obj to step. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
3D viewer and converter with huge file type support
A 3D model converter
A CAD converter with huge format support
A widely-used 3D animation application from Autodesk
A set of 3D modeling tools
A converter for 3D formats
A dedicated CAD converter
Multiplatform software - convert obj to step on any platform
3D CAD/CAM tool for product development
An open source multiplatform 3D CAD/MCAD/CAx/CAE/PLM modeler