Does anyone know of a way to use a DWF to be a boundary for a hatch without having to trace around the points with a polyline?

A little bit more info about it, we have received a plant layout from a customer that is a 2D export from a 3D design (not sure what program they are using), we need to hatch around areas of the plant for some drawings.

I have tried to plot their layout as a PDF and use PDF import and flatten (because the hatches didnt find a boundary)

Does anyone else have any ideas?