Sunil,
As I also said, I prefer remodelling. For that reason (and because of infrequent use) I have not gone far into importing. What I use - if I do - is an unspecialized Corel Trace. This came with my installation of Corel (-Draw, -Photopaint, ...) and is "general purpose", which also means : not specialised. But it has some settings as to quality, number of segments, preferences towards lines or curves, etc.
So in the case where I want a scanned drawing to be present in a project (mostly as geometric reference to do other things) I would use Trace to produce vector geometry, export this to DWG, scale properly and import into CAD. This geometry can be visual reference only or be used as a base sketch that is used to attach keypoionts of created geometry. Taking the case of an electronic print that is needed to be incorporated in a housing, tracing will produce a number of line segments for a round hole. Creating a circle through 3 points I can attach to the scan in an acceptable way.
I know that there are specialised programs around that do a far better job. They will try to discriminate lines based on thickness and/or color, recognise text, etc. Look around on the web, you'll find plenty of offers. Try them out to decide what suits your needs.
Alex
