How can I open and use a drw or pdf file that was create using AutoCad?

AutoCad files in Draw

There only appears to be an AutoCAD filter for DXF files and not DRW. If you can export the AutoCAD files in this interchange format you will likely have better results in Draw. Bug fdo#63054 seems to indicate that PDFs generated by AutoCAD may fail with a “General I/O Error” when opening with Draw. Is that what you are seeing?