Printer not working, libcupsfilters built against older version of qpdf
/var/log/cups/error_log
error while loading shared libraries: libqpdf.so.29: cannot open shared object file: No such file or directory
$ ls /usr/lib/libqpdf*
/usr/lib/libqpdf.so /usr/lib/libqpdf.so.30 /usr/lib/libqpdf.so.30.0.0
$ pacman -Qo /usr/lib/libqpdf.so.30
/usr/lib/libqpdf.so.30 is owned by qpdf 12.0.0-1
# check-link-consistency
ERR libcupsfilters 2.1.1-2 /usr/lib/libcupsfilters.so.2.0.0 libqpdf.so.29
Downgrading the package qpdf (12.0.0-1 => 11.10.1-1) fixed the problem and the printer worked again.