I don´t want users to print using the standard print button of Acrobat. To do that, I used the PDF security functionality (in File | Form Properties).
I do want, on the other hand, the users to print using a custom button on the form that uses the xfa.host.print function. However, I realise that this function will not work due to the first parametrization.
Is there a way to enable the second functionality while maintaining the first one.
You could hide the print button on the toolbar. See the hideToolbarButton() method in the Acrobat JS Guide. However, that won't stop a savy user from doing a standard print. The only way to do that is to disable any printing at all (including your custom button) and even in that case, it wouldn't stop someone from taking a screen shot and printing that.
Nope. Hopefully there will be in the future, but currently there is no way to accomplish what you want. Best you can do is hide the toolbar button and file menu item and hope the user doesn't know enough to find a way around it.