Merge pdf files and automatically create a table of contents with each file as an entry

I have several pdf files (chapter1.pdf, chapter2.pdf, etc.), each one being a chapter of a book. I now how to merge them into a single pdf (I use the command pdfunite from poppler), but since the output file is big, it's difficult to find a chapter without having them indexed in a table of contents. So how to create an embedded table of contents in which each merged chapter is an entry? Note that I do not want to create a page in the output file which contains the list of chapters and their respective page numbers. I want the index/table of contents metadata of an pdf file, that can be browseable in any pdf reader's (or ebook device's) which supports such feature.