I saw this question flying around the other day and thought it was kind of interesting. Someone was asking about the cool new thumbnail previews you get for items in search results in SharePoint 2013. They really liked how Microsoft Office documents work and wanted to be able to do the same thing with PDF files. There was an answer, which is a good one, that you could create a custom WOPI extension that would render PDF files using Office Web Apps. The drawback to that is that it requires someone to do some coding and testing (using full trust code), then deploy it to your OWA farm, then create a new WOPI binding in the SharePoint farm. Again, an entirely reasonable response if your requirements dictate that.
I, however, representing all that is good about being lazy and cheap, decided to take a different approach to this. Without digging into the particulars of how all the plumbing works, at the end of the day a search results preview for Office documents are just done via an iFrame. So why not do the same thing for PDF documents? Why not indeed - that's exactly what I did. Here's all I did to make this work:
That's it - now you're ready to go. One thing to point out here - in step 1b I configured the display template to use the hover panel that comes out of the box for sites. It is configured to use an iFrame and render it nice and pretty, so I didn't even have to create a hover panel for it. As a side note I actually DID do that when I was fooling around, but the out of the box stuff looks so much better than what I can do I figured why fight it - graphical beauty ain't my thing. Once it's done I get a nice preview for my PDF documents in search results, which you can see here:
That's all there is too it. I've attached my display template here, just in case you are as lazy and cheap as I am. :-) Hope everyone has a Merry Christmas and Happy New Year.
UPDATE: I did discover one big limitation with this approach - it only works if your PDF documents are in the same host as your search center, i.e. if they are in the same web application is the easiest example. So if you have your search center at http://www.foo.com, but your PDFs are in http://www.bar.com then they will not be displayed as preview items. That's because of some X-Frame-Options headers that we send down with SharePoint now. If you are following our new recommendations for SharePoint 2013 to use a single web application for your farm then you will be fine, but if you have multiple web applications or are crawling content from non-SharePoint sites then it will not render in the preview.
Couple other possible gotchas to be aware of - 1) make sure you have installed the Adobe reader on the machine on which you are viewing the previews and 2) I've got at least one report saying this doesn't work in a non Internet Explorer browser.