My first instinct was to google for pyPDF. Success! So, fore go reading any doc and just give the old easy_install a try.

$ sudo easy_install pypdf

Another success! Ok, a couple help() calls later and I am ready to go. The end result is surprisingly small and seems to run fast enough even for PDFs with 50+ pages.

from pyPdf import PdfFileWriter, PdfFileReader

def append_pdf(input,output):
    [output.addPage(input.getPage(page_num)) for page_num in range(input.numPages)]

output = PdfFileWriter()
append_pdf(PdfFileReader(file("sample.pdf","rb")),output)
append_pdf(PdfFileReader(file("sample.pdf","rb")),output)

output.write(file("combined.pdf","wb"))