you should first consider copy your file.
Then, make a CUT PLANE and cut your model at the desire intersection.
Choose your desire parallel view and "make2D"
Then, clean your draw and export to Illustrator or DWG - remember to keep in mind that CIRCULAR and OVAL chapes wont be read as perfect inside Illustrator or Autocad. You will need to make small adjustments if you find so.
And of course.. Batting hatch (for insulations) wont be read between this softwares. You will need to add them inside Autocad with a metafile export. Then import again to your Cad file.