import com.ironsoftware.ironpdf.PdfDocument;
import com.ironsoftware.ironpdf.bookmark.Bookmark;
import com.ironsoftware.ironpdf.bookmark.BookmarkManager;
import java.io.IOException;
import java.nio.file.Paths;
import java.util.List;

// Load an existing PDF from the file system (or create a new one from HTML)
PdfDocument pdf = PdfDocument.fromFile(Paths.get("assets/book.pdf"));

// Add top-level bookmarks to pages of the PDF using their page indices
BookmarkManager bookmarks = pdf.getBookmark();
bookmarks.addBookMarkAtEnd("Author's Note", 2);
bookmarks.addBookMarkAtEnd("Table of Contents", 3);
bookmarks.addBookMarkAtEnd("Summary", 10);
bookmarks.addBookMarkAtEnd("References", 12);

// Retrieve a reference to the Summary bookmark so that we can add a sublist of bookmarks to it.
List<Bookmark> bookmarkList = bookmarks.getBookmarks();
Bookmark bookmark = bookmarkList.get(2);
bookmark.AddChildBookmark("Conclusion", 11);

// Save the PDF to the filesystem
pdf.saveAs(Paths.get("assets/bookmarked.pdf"));