# pdf拆分
pdftk ORIG_FILE.pdf cat 1 5 7 10-12 output NEW_FILE.pdf
# pdf合并
convert -density 300x300 -quality 100 mine1.pdf mine2.pdf merged.pdf
gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=merged.pdf mine1.pdf mine2.pdf
# low resolution
gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -dPDFSETTINGS=/prepress -sOutputFile=merged.pdf mine1.pdf mine2.pdf