DXF is an ascii format for the transfer of 2D (and primative 3D) mechanical data between CAD platforms. Developed by Autodesk in the early 80's. Even though 3D is becoming the norm in mechanical design, there is still a requirement for the transfer of 2D information such as Logo's, outlines, areas etc and this is where DXF comes into its own. I have provided a link below to the DXF site, it is worth getting a basic understanding of the format as you will use it, I have done a lot of Autolisp programming in the past so have an understanding of the format. So a simple explanation:-|
A 2D polyline is a continous line made up of numerous segments joined together and either open (a path) or closed (an outline), (in PCB land we use 2D poly lines for board outline, areas, templates etc), these lines have x,y co-ordinates. A 3D poly line is similar to a 2D polyline except it has x,y and z co-ordinates. The DXF filters for most PCB programs are quite simple and can only handle certain entities in the DXF file, one of these being 3D polylines. The software that has exported the DXF data has by default output the Polyline as a 3D entity. If the program can output an early version of DXF such as Release 12 it may solve your problem.
Hope this helps a bit.
Everything you might want to know about DXF
**broken link removed**