CAD to PDF Not Responding

CAD files can have many layers and complex vectors which can be too much for Acrobat to handle. Try turning off any unnecessary layers in CAD before exporting to pdf, is there an option to rasterize complex vectors when exporting? that may help. Do you have Illustrator? can you open the DWG there and save as pdf? You may want to simplify the objects in Illustrator (Object> Path> Simplify) or save the complex vectors as a high-res image. You could also save as a PDF and run an Acrobat preflight to Convert smooth lines to curves. These methods should reduce the number of vector anchor points and reduce the file size. Also, try unchecking Preferences / Accessibility / Enable assistive technology support. And check for Acrobat updates under the Help menu.