I freshly installed 16.04 and the cups-pdf printer 2.6.1-21.
Everything works fine, I can open the pdf in Ubuntu w/o problems in every program, e.g Master Pdf Editor 3, can send it as email att. and it opens fine in Android etc.
But as soon as i try to send it as attachment to a whatsapp-msg, the pdf is not accessible. In Whatsap-Web it can't be uploaded with the message:
"Impossibile inviare questo documento perché il formato non è supportato" (i.e. unsupported format)
I tried different options, even re-print as flattende pdf, but without luck. In 12.04 with the older cups-pdf version i never had this issue.