In the model you can create a sketch and text is an option in the Draw panel. Make a text object, select the font and size you need and then use Extrude to "cut" the text into the object. Then use the Export command to export a STP file.
If I understand correctly this is what you want.
Stuart Kinzel Inventor 2013-64bit, HP EliteBook8740w Intel Core i5CPU 2.67 GHz 8GB memory Windows 7 64bit
Yes, Extrude or Emboss is the simplest way. But plastic parts needs add a draft and it is a real pain in the.... For CNC machines is enough to use wires as a toolpath and the tool makes shape inclusive draft and fillets.