Yes, you can use Didger to digitize contour lines. If you have a paper map, you can either digitize them using a digitizing tablet or you can scan the map and import it into Didger to digitize on-screen.

The first step is to calibrate the tablet (Draw | Tablet | Tablet Calibration), or register the image upon import in the Image Registration and Warping dialog.

After the paper map or image is calibrated, draw polylines to digitize the contours by clicking Draw | Polyline. When you digitize the contours, enter the contour value as the Primary ID for the polyline.

Didger also has the ability to automatically digitize lines from an image (Image | Vectorize Image), so you don't have to manually digitize the contours. 

For more information, see here: 

Updated August 16, 2018