How to digitally sign with my Qualified Certificate in Acrobat Reader on iMac?

[tomasv60945811]

I have to sign some documents with Qualified Certificate CA 4 on my iMac.

So I imported the third party issued certificate to the System Keychain and set it to "Always Trust" everywhere.

Then I imported the certificate to the Acrobat Reader - Preferences - Signatures - Trusted Certificate.

But when I put Digitally Sign with certificate, the certificate doesn't show up, just the notification: This signature field requires a digital signature identity.

Can anybody help me please, what have I missed? Thx