A handy-dandy Perl script that splits double page pdfs. 

TO USE:

   You need to have PDF::API2 installed. To install run 
       cpan PDF::API2
   Use the filename or directory containing the pdfs to be split. For example
       ./pdfSplit ~/Desktop/
             or
       ./pdfSplit ~/Desktop/myfile.pdf

Adapted from http://snipplr.com/view/18924/split-crop-double-page-pdfs-in-two/