you either need bobart to do that in bobcad or you need something like Corel Draw graphics X3 which you can down demos of to try open a new file and import image into corel and save as dxf. Corel will let you save but bobart demo will not if you want post a jpeg and I'll do a quick conversion to show you
If your using a font and download Corel Graghic x3 one of the programs is called Bitstream Font Navigator. With this you van load font into Bobcad and use as text and then vectorize it. That what I do anyways.