DXF file not to scale in Blender

When I open the DXF file in LibreCAD, then it shows the correct size of an object, but when I import that file in Blender, then the size of that object becomes very large.

Your DXF file is using 1 unit == 1 inch, so the marked length is $$11\cdot 12 + 11.2780 = 143.278"$$ long. Blender's internal unit is 1 meter long, so the DXF imports as 143.278 meters, and $$\frac{143.278}{0.3048} \approx 470'$$ which is what's being displayed.