This article shows how to search a string in a whole pdf file.

With this method you can use a PDFDoc instance to search a word in a whole pdf file and store/menage results.

public void customSearch(PDFDoc doc, String search)
 {
    bool caseSensitive = false;
    bool wholeWord = false;

    for (int i = 0; i < doc.PageCount; i++)
    {
       PDFPage page = doc.GetPage(i);
       page.ObjsStart();

       // find in page
       PDFFinder finder = page.GetFinder(search, caseSensitive, wholeWord);

       // manage each search term contained in this page
       for (int c = 0; c < finder.GetCount(); c++)
       {
          // start position
          int firstCharPos = finder.GetFirstChar(c);

          System.Diagnostics.Debug.WriteLine("PAGE:" + i);
          System.Diagnostics.Debug.WriteLine("Position:" + firstCharPos);

          // do custom actions
        }
      // close page
      page.Close();
    }
}