Python code to concatenate PDF files, just keep them ordered by name, like pdf_01, pdf_02, pdf_10...

concat_pdf.py

from pyPdf import PdfFileWriter, PdfFileReader
import os

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

output = PdfFileWriter()
for pdf in filter(lambda x: '.pdf' in x, os.listdir('.')):
    append_pdf(PdfFileReader(file(pdf, "rb")), output)    

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