When you mention disconnected blocks, were you reading the dxf into AutoCAD or similar?
When I used it I read the resulting DXF into a Pro/E drawing for cleanup.
PDF doesn't save primitives for geometry; everything is converted to curves - arcs, splines, whatever. The result will mostly require some attention.
The best use I made was for a computer motherboard with all its components and hundreds of pins. Converted well and was useable, but replacing the curve pieces with circles at the pins cut the clutter immensely.
If the reason for the DXF is to program CNC from, then editting is definitely going to be required.