I would like to use both Chrome's built-in PDF viewer and the Adobe Reader plugin at the same time. Specifically, I want to open PDFs with the built-in viewer by default (because I think it is more secure), but use Adobe Reader for some special internally generated PDFs that use features the built-in viewer does not have.

I have two questions:

First, is there a halfway sensible way to do this? I have noticed that Chrome only allows one of the plugins to be active at any time, probably because they conflict in their support for application/pdf content.

Second, what do you think about the following: My solution needs to work only on Windows, and there is a difference in how NPAPI plugins work on Windows and elsewhere. On Windows, the supported MIME types are stored in a resource, which I can modify. It turns out that by changing the application/pdf entry in the list of MIME types to something else, I can achieve my goal:

  • Chrome allows me to enable both plugins at once
  • It uses the built-in PDF viewer for any normal PDF
  • When I request something that is actually PDF, but has the different Content-Type I put into the resource, Chrome loads it in the Adobe Reader plugin

I am unsure whether this is a "halfway sensible way", so I may not actually have answered my own question. The main issues I can see are:

  • I have no guarantee that Adobe will not change the way the plugin identifies incoming content in the future. While it works now, some future release may stop treating the content as PDF because it has an unknown content type
  • It breaks the digital signature on the plugin DLL
  • It most likely violates Adobe Reader's EULA to "distribute" a modified file, even if only internally

What (else) can go wrong?

  • This does seem like a reasonable solution, however, sending the wrong mime-type for a file feels like a dirty hack. – MrWhite Feb 18 '13 at 14:53
  • +1 With Firefox always looking to ape Chrome and eventually planning to replace external PDF plugins with PDF.js, a workaround might be required for it as well. – Karan Feb 18 '13 at 20:01

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