For those having LaTeX (or TeXShop) installed there is also the command 'texexec' that does what was requested (combing jpg's) and much more. For PDF it is almost miraculous: selecting pages, reformatting, resizing, splicing and combining pages into one pdf file, etc. (see e.g. http://www.eskimo.com/~c/debian/tetex-manpages/texexec.1.html). With OS X's orientation towards PDF, this is a valuable tool. Eduard.