With August 2015 CU for SharePoint 2013 Microsoft added cloud hybrid search capability to SharePoint Server 2013.
With cloud hybrid search, you index all your crawled content, including on-premises content, to your search index in Office 365. When users query your search index in Office 365, they get search results from both on-premises and Office 365 content.
For more information about cloud hybrid search, including how to configure it, you need to join the Microsoft® cloud hybrid search preview program.
After you have joined the program you can use the following link to access the documentation for the cloud hybrid search feature: https://connect.microsoft.com/office/program8647.
Be aware that August 2015 CU for SharePoint 2013 contains the required changes for SharePoint 2013 to enable this feature. The hybrid search functionality itself will be available as a preview in Microsoft Office 365 starting on September 7, 2015.
KB 3080169 – Cloud hybrid search capability in SharePoint Server 2013
I have setup an Hybrid Search environment on SharePoint 2013 and SPO. Currently my Search Center is on On-Prem. I am getting both On-Prem and SPO docs on On-Prem search result page. All the settings and search result looks good.
However i am not able to Preview PDF docs coming from SPO. Preview is working for all MS office docs from SPO. I have tried to change the On-Prem search result type for PDF files to consume Word Item as display template but still not working. My issue is only with PDF preview not working from SPO files on Serach center which is on On-Prem. Can any one give valuable input to resolve this issue ?