DLF is a file extension associated with DataCAD (which also uses its native AEC format). DataCAD is an advanced CAD software for architects that offers 3D rendering capabilities.

DLF files are used by DataCAD to store double precision layer data. Official DataCAD forum offers a comprehensive documentation on this format. DataCAD debuted more than 40 years ago. Software license costs overs 1200 USD, but a 30-day free trial is available.