To add bookmarks to pdf using iTextSharp, you must use Chapter and / or Section objects. Although you can technically do this work, the Chapter and Section objects have some limitations and some fairly large overhead, especially for 1000 items. In addition, I never managed to display the section and section numbers in my document, which is probably a problem for you if your content is in pdfpcells.
This link gives a good idea on adding bookmarks to pdf. Scroll down to the end of the bookmark article.
This article also contains information on installing LocalDestinations in pdf. They are not displayed as bookmarks, and they require both the "Goto" link and the "Destination" link. Thus, if you want or can create an index page in your pdf, this might be the best solution. Your index page will contain all the "Goto" links, and the content in your pdfpcells will be LocalDestinations.