Hi,

We are looking to achieve some more custom option, links, description and details in document Preview dialog in search page in SharePoint 2013 online (Office 365 E3 version). Actually, once user view document in search page, so in document preview page, we wanted to add some more custom option, links, description and details.

Any information, challenges, codes about this would be greatly appreciated. Thanks!

The way to do that is through Search Display templates. These are well covered in a lot of different places:

https://support.office.com/en-us/article/Change-how-search-results-look-by-using-result-types-and-display-templates-0fc83eeb-28c8-4f65-afe3-0ee515296a9d

http://blogs.technet.com/b/sharepoint_quick_reads/archive/2013/08/01/sharepoint-2013-customize-display-template-for-content-by-search-web-part-cswp-part-1.aspx

But there's loads of information out there on this.