Creo 4.0 now reads the unit of imported DXF files in 3D models (defined by value of $INSUNITS)
So if the DXF unit is not the same as your part setup, the geometry is wrongly scaled.
Unknown problem in previous releases...
PTC workaround is to edit the DXF file to change the $INSUNITS value.
Not acceptable for users in 2019.
Please provide import conversion functionality for this case, as it exist in other softwares...