Bookmarks

I have an app that creates a PDF document using iTextSharp. After the document has been created I need to add bookmarks to it. I don't want to add any extra pages I just want bookmarks that will take to user to a certain page when they click on it. I have found lots of examples online but I haven't been able to get it working. I'm aware I'm supposed to use the PdfOutline object but I've been trying different examples for days and can't get it working. Just to get me started could someone tell me how to add a bookmark structure to an existing PDF document without adding any extra pages. eg the following structure for a 5 page document:

|---Page 1
|      |
|      --- Page 2
|      |
|      --- Page 3
|
|---Page 4
|      |
       --- Page 5

Thanks in advance