To add to Keith's comments, there will always be distortion of the media, even for the simple fact that humidity is present in the air... will be absorbed by blueprints. We have also seen scanners that were stretching the media along the major axis when feeding! More expensive exercise, but if accuracy is crucial, better redraw. The only time we have seen scanning as worthwhile is for large companies wanting to keep 1000's and 1000's dwgs drawn manually in past 100 years, and want to keep 'm as historical records - not to be used/modified... It is easier to fit them on few CDs than having to rent many rooms for plan storage [or at least to reclaim that wasted space].