How to force to show PDF in google chrome using Adobe PDF Plug-In only
There's no way for a website to force the browser to use one renderer or another: those decisions are all made client-side. As you noted, disabling the Chrome PDF plugin bubbles the Adobe plugin to the top, but that's a decision the user would have to make.
That said, if you have a PDF with rendering issues that you can share, please file a bug at http://new.crbug.com/. I'll be happy to put it in front of the correct team for triage.
The only way that you can be 100% that all users can open your PDF correctly currently, is to force that the PDF is downloaded.
Use some headers within your apache or backend.
Example for Apachehttps://stackoverflow.com/a/11991050/3086639