DXF

DXF (Drawing eXchange Format) is the file format developed and maintained by Autodesk® for the exchange of 2D/3D CAD data in an AutoCAD® drawing with other applications. It has been adopted as an industry standard for this purpose, with widespread support for reading and writing DXF files across CAD/CAM/CAE and other technical applications (such as CNC machines).

DXF files generated by Visual integrity software can be imported and edited in AutoCAD and other packages such as Microstation®, UniGraphics® and PowerShape®.

• DXF output is compatible with AutoCAD 2000 and later
   
• PS/PDF curves are converted based on splines (not polylines) for better usage of contour information and path quality
   
• Supports vector graphics and font text, embedded raster images are extracted to TIFF/JPEG files and referenced in the DXF output
   
• Option to keep, outline or remove hatches/fills during conversion

Innovene, the petrochemicals division of British Petroleum, uses pdf2cad to convert PDF into AutoCAD files so that they can modify instrumentation and electrical drawings.  
product = pdf2cad

The Mitsui Engineering & Shipbuilding Company's engineering subsidiary in Thailand (MPS) uses the PDF FLY production server for high-volume batch conversion of PDF drawings into the DXF format.
product = FLY Batch

Delcam added an option to import PDF and PostScript into PowerShape by scripting command line calls to the PDF FLY executable.
product = FLY SDK