DocumentViewer.SearchOptions property allows you to do a auto full text search and highlight keywords in the viewer. SearchOptions settings are also reflected as default values in the UI.

If you specify SearchOptions.Term, an automatic search will be done when the document is displayed, i.e. the specified term will be searched and results with clickable positions will be listed on the left pane and the term will be highlighted in the pages.

For example, if you launch the document viewer from a search results page, you can pass the same search term to the viewer.