Split, Merge, Convert PDF

[NoiSNC]

Split pdf

(sample study carefully)
gs -sDEVICE=pdfwrite -dNOPAUSE -dBATCH -dSAFER -dFirstPage=22 -dLastPage=36 -sOutputFile=outfile_p22-p36.pdf 100p-inputfile.pdf
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split multipage pdf to single png

convert -quality 100 -density 300x300 input.pdf page.png
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To merge two pdf files, file1.pdf and file2.pdf:

gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=finished.pdf file1.pdf file2.pdf
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Convert pdf to png

convert -quality 100 -density 600x600 p.pdf p.png