pdnsutil import-zone example.com db.example.com

See the official documentation for more information: Migrating (Signed) Zones to PowerDNS

pdnsutil import-zone-key example.com Kexample.com.+014+03070.private ksk

pdnsutil import-zone-key example.com Kexample.com.+014+22663.private zsk

I didn't know about this keys anymore. I found them under /etc/bind/keys. I found the description in the content of the *.key files.

root@dnsserver:/etc/bind/keys# head -n 1 *.key
==> Kexample.com.+014+03070.key <==
; This is a key-signing key, keyid 3070, for example.com.

==> Kexample.com.+014+22663.key <==
; This is a zone-signing key, keyid 22663, for example.com.