Dear Maintainer,

calling

separate -f 9 -l 10 sek2_biologie.pdf sek2_biologie_%2d.pdf

results in

Syntax Error: 'sek2_biologie %2d.pdf' must contain '%d' (or any variant respecting printf format) if more than one page should be extracted, in order to print the page number

even though this should be an acceptable variant of a Print F format string.