Adds a bookmark for the current page. Bookmarks usually appear in PDF-Viewers left of the page in a hierachical tree. Clicking on a bookmark will jump to the given page.
The parameter parent is another bookmark which is used as the parent of the new bookmark. If open is unequal to zero the bookmark will be shown open by the pdf viewer.
The bookmark has no meaning if the document is printed or viewed but it will be used if the document is converted to pdf by either Acrobat Distiller™ or Ghostview.
The returned value is a reference for the bookmark. It is only used if the bookmark shall be used as a parent.