Improved: When using DocumentViewerMatchOptions.MatchAnyWord, now the quotation marks can be used to specify phrases
inside a query that is set via DocumentViewerSearchOptions.Term.
For example;

• red "four wheels" petrol will match red or four wheels or petrol or red four wheels petrol

• red ""four wheels"" petrol will match red or "four wheels" or petrol or red "four wheels" petrol

• C#

  documentViewer.SearchOptions.Term = "red \"four wheels\" petrol";
  documentViewer.SearchOptions.MatchOptions = MatchOptions.MatchAnyWord;
  
  //If you have an array of phrases, you can surround them with quotation marks 
  //and then join them with spaces to form a query:
  var phrases = new[] { "red", "four wheels", "petrol" };
  var query = string.Join(" ", phrases.Select(p => $"\"{p}\""));
  documentViewer.SearchOptions.Term = query;
  documentViewer.SearchOptions.MatchOptions = MatchOptions.MatchAnyWord;

Note that two consecutive quotation marks "" can be used to escape, i.e. to search for a quotation mark literally as ".
The same feature can also be used in the Viewer's Find dialog.