We have listed custom document links in our custom page.
Our users want document preview, just like search document preview, on our custom link when hovering a tag.
How can this be done?
Sharepoint 2013 introduced the Callout framework similar to the Dialog framework they introduced in Sharepoint 2010. The good news is the callout framework can be extended and customized as you need.
Apart from search, you see these callout previews also in Document Library,Assert Library,Task Lists etc.
There is good tutorial of working with Callouts here.
For your case, you need a Callout with document preview which is a slight modification by using the
IFrame to display document previews.
The complete step by step implementation is available here.
Did you try Office Web App. When you configure office web app with you SharePoint than automatically it will crawl all your search and it will start showing preview. Office web app is free for preview but if you need edit option than you have to get licence for it.
Go through this link for more information http://www.harbar.net/archive/2012/07/30/353.aspx