Merge more PDF files into the one
pdftk /my-directory/file* cat output /tmp/result.pdf
Rotate all pages
pdftk /tmp/in.pdf cat 1-11south output /tmp/out.pdf
PDFTK (PDF Toolkit) is the command-line open-source tool for editing PDF files.
pdftk /my-directory/file* cat output /tmp/result.pdf
pdftk /tmp/in.pdf cat 1-11south output /tmp/out.pdf