Não encontrei nenhuma maneira de salvar explicitamente um intervalo de páginas, por isso optei por excluir o restante.
# Extract and save each page in its own file
pages=$(djvused -e 'n' "$if")
for ((i=1; i<=$pages; i++)) ;do
of="${if%.*}.$(printf "%03d" $i).djvu"
djvused -e "select $i; save-page-with \"$of\"" "$if"
done
# Remove one page from an existing djvu file
djvm -delete "$if" 2 # remove page 2
# Save pages 3-6 to a new file, by removing
# all other pages from a copy of the original
from=3; to=6
of="${if%.*}.$from-$to.djvu"
cp "$if" "$of"
pages=$(djvused -e 'n' "$of")
for ((i=$pages; i>$to; i--)) ;do djvm -delete "$of" $i ;done
for ((i=1; i<$from; i++)) ;do djvm -delete "$of" 1 ;done