I needed to merge (concatenate) some PDF files and couldn't find any applications for OS X. Acrobat surely does it, but is very expensive to buy for just one single merge. Office v.X can include PDFs and print the whole document in PDF, but the output was very large and in poor resolution ... and so on.
Finally I tried pdflatex and it worked great! Just create a little .tex script that uses /includegraphics{file1.pdf} for every single page, and the output file is small and in very good resolution.
[Editor's note: The above is exactly what was submitted by the anonymous contributor, and I couldn't ask any clarifying questions as he/she did not include their email address. Based on some web research on my part, it appears that you'll need to install TeXLive-teTeX in order to get pdflatex. However, I haven't tested this out by actually installing the package myself, so you're on your own on this one -- but I thought the hint interesting enough to merit posting anyway.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020714102702896