Search string in Documents and highlight the searched strings in the Document

Hai,
  We are presently working on C# windows Application using Janus Controls.
       In that we have a search functionality like, if you search any word in search box, all the documents(it's my be Notepad,Ms-word,PDF) which contains that searched word should be displayed in the application.

when we Double click on the any document it should open a new window and show preview like what word you have searched and the searched word should be highlighted with some color as like in our Microsoft Word Document.

we can open the particular document using word or Pdf and highlight the text. But we need to open it in one window and show all the matched searched text in highlighted.
     Please provide the possible Solution or link to work with or any tools to work with this scenario.