As long as you know the dimension of one thing within the drawing (the overall length of a wall, the width of a door, etc.) import it as you're doing and then just do an Enlargement (Edit/Enlarge/(set the center)/Enlargement/Cal. Dist.). If you're trying to do it when you import it you'll have to play around a little - it could be by a factor of 12, but then it could also be by a factor that is some wacky number too. With the Enlargement trick you have full control over what you're using as the control dimension.
Good luck!
Highest Regards,
Alan T. Hendry, RA
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