Fast PDF splitter library

mbtPdfAsm is a fast, open source command line tool for PDF processing.

Xpdf is also worth mentioning since it's GPL and written in C++. The source code is well modularized and allows for writing command line tools.

Does it have to be python? My pure-Perl library CAM::PDF is pretty fast at appending and deleting PDF document pages. It saves the sweeping for the very end, where possible.