I found two command lines for Dragon:
-no-sandbox and
-safe-pluginsIn Chromium, the renderers are always target processes, unless the -no-sandbox command line has been specified for the browser process. It is also possible to run the plugin processes inside a sandbox target, using the -safe-plugins command line.
http://dev.chromium.org/developers/design-documents/sandbox-safe-plugins works with Flash Player, but not with Acrobat, the only plugins I have tested.
Edit:-safe-plugins -trusted-plugins=nppdf32.dll makes Adobe Reader/Adobe Acrotbat work.