.dxf Drawing Interchange Format , or Drawing Exchange Formats (dxf) supported by Qcad.org
Note: Most CAD programs can export to .dxf

Read only formats:

.pdf .fdf
All image formats .jpeg .png .tiff

Other Compatible formats:

.svg .svgz Inkscape
.doc
.dwg
.xls .ots, .odt .ods .sxw, .sxc, .docx See ISO 26300 and Open document formats. for more information.
.txt Text format
.odg OpenDocument Graphics format