Stapler is a pure Python alternative to PDFtk, a tool for manipulating PDF documents from the command line. Like pdftk, stapler is a command-line tool.
With select, you can cherry-pick pages from pdfs and concatenate them into a new pdf file. The delete command works almost exactly the same as select, but inverse. It uses the pages and ranges which you didn't specify. The split command splits the specified pdf files into their single pages and writes each page into it's own pdf file. With zip, you can cherry-pick pages from pdfs (like select). The pages from each pdf are merged together in an interleaving manner. This can be used to collate a pdf with odd pages and a pdf with even pages into a single file. The info command shows information on the metadata stored inside a PDF file.