% fink install ghostscript6
and then (after issuing a rehash):
% gs -q -sPAPERSIZE=a4 -dNOPAUSE -dBATCH -sDEVICE=pdfwrite \
-sOutputFile=output.pdf pdf1.pdf pdf2.pdf
The command above (it's one line, as shown by the \) will basically create one outputfile called output.pdf that consists of pdf1.pdf and pdf2.pdf. You can replace pdf1.pdf with *.pdf and it will grab all the pdf files and output one pdf. That's all.
[robg adds: I haven't tested this one...]

