this might be a little specialized but i use corel generally to layout architectural drawings. I export them from autocad usually as a .pdf with a variety of different line weights, I notice its not the .pdf but corel tends distort or alter these line weights which typically undoes hours of hard work, is there a way to make these line weights transfer more smoothly to corel?
Have you tried exporting your drawing as an EPS or DFX and importing it.
I have no experience with CAD software but it's worth a try.
Does this also happen when you are importing the Original DWG file?
i have tried .eps, and i dont really remember it being too much better.. i dont think a dxf would work because the way i use autocad is to assign line weight by colour of the object, so the line weight is not applied until you post script it, ie eps or pdf.