Suppose you have several papers, say, of Eshelby, in pdf format. Suppose you want to make the collected works of Eshelby using these pdf. Here is a page that tells you how to go about doing it. It works exactly as the page says it should; however, there was a small tweak I did in the second script. Since the page numbering is used as the background, sometimes, for some pdf files, the page numbers are not visible. That can be overcome by making the pages as background and writing the page number on this background. Of course, when you have a collection of pdfs with not all of them having the same written area, a little bit of tweaking of the page height etc are needed to make sure that on all pages the title (Eshelby: Collected Works) and the page number are such that they are not overwriting any text. Have fun!
A pdftk + LaTeX tip that I learnt today!