To cut a pdf of whole proceedings or book into contributions/chapters. you can use
pdftk – A handy tool for manipulating PDF
https://www.pdflabs.com/tools/pdftk-the-pdf-toolkit/
What I use is
pdftk inputfile.pdf cat firstpage-lastpage output outputfile.pdf
You can do it one-by-one; I usually prepare a file like
pdftk MPI.pdf cat 3-9 output MPI_3.pdf
pdftk MPI.pdf cat 11-19 output MPI_11.pdf
pdftk MPI.pdf cat 21-29 output MPI_21.pdf
pdftk MPI.pdf cat 33-40 output MPI_33.pdf
pdftk MPI.pdf cat 41-49 output MPI_41.pdf
pdftk MPI.pdf cat 51-56 output MPI_51.pdf
pdftk MPI.pdf cat 57-65 output MPI_57.pdf
pdftk MPI.pdf cat 67-74 output MPI_67.pdf
pdftk MPI.pdf cat 75-77 output MPI_75.pdf
and run it as a shell-script.