censor-pdf.sh

# prerequisite: create $censored_pdf from $original_pdf using chrome print pdf -> tick 'print as image' (linux chrome) -> save as pdf

# split
for page_range in ${original_page_ranges[*]}; do
    pdftk $original_pdf cat $page_range output $page_range.pdf
done
for page_range in ${censored_page_ranges[*]}; do
    pdftk $censored_pdf cat $page_range output $page_range.pdf
done

# merge
both_page_ranges=("${original_page_ranges[@]}" "${censored_page_ranges[@]}")
sorted_ranges=`echo ${both_page_ranges[*]}| tr " " "\n" | sort -n`
ranges=`for name in ${sorted_ranges[*]}; do echo "$name.pdf"; done`
pdfunite $ranges censored.pdf

example.sh

original_pdf=uncensored.pdf
# prerequisite: create $censored_pdf from $original_pdf using chrome print pdf -> tick 'print as image' (linux chrome) -> save as uncensored-image.pdf
censored_pdf=uncensored-image.pdf
original_page_ranges=("1-2" "5-6")
censored_page_ranges=("3-4" "7-8")
source censor-pdf.sh