For imported DWG and DXF files, you can specify the units of measure for the imported geometry, and define a scale factor to achieve the appropriate scale for the 
  Revit project. 
-  Select the imported CAD file and click Modify | <File Name> tab
Properties panel
 (Type Properties). 
  Note:  SAT and 3DM files can't be scaled. 
  
 
- In the Type Properties dialog, modify Import Units or Scale Factor. 
  
If you change the import units, the scale factor automatically updates. See 
	 Import and Link Options. 
  
 
  Note:  If no values display for these parameters, you must reload the link or re-import the file. 
  
 
 
- Click OK.