I am told that if you protect any document with AIP and then save it as PDF, the protection is gone.
I created a document with a custom label with following permissions.
View Content, edit and save, Print
Recipient got the document , he couldn't copy data from document as it was restricted.
He printed the file to PDF and post that he could copy the data and in PDF properties, security shows no restriction. And he can send it to anyone else who was not supposed to have the access to the file?
And when we protect the PDF file, it changes it to PPDF and reciepient need to download an app to open the protected PDF?
Don't give him permissions to Print. It's not just PDF you will have issues with, thare are many other "virtual printer" applications that can convert filetypes to different formats, as long as you are able to print them.
In general, I would advise you to post this to the AIP Yammer network, where you can get direct answer from the Micorosft folks repsonsible for the feature implementation: https://www.yammer.com/askipteam/