Automating Password Encryption of PDFs using Acrobat Pro

Hello There. I have recently been evaluating Acrobat Pro for several colleagues in my business area. 

The requirement is to automatically produce PDFs with unique passwords as per the title. The originating application is Excel. The previous solution used an app which is depracated in the organisation, but like Acrobat Pro provided a printer interface, through which you could specify the password when your PDF was being created, automating the process with VBA.

I've run out of evaluation period, so I can't experiment further, but I haven't been able to do this quite simple, extremely reasonable thing with Acrobat Professional. The only way to specify a password within Acrobat seems to be typing it by hand; Here are some of the things I tried:

- You can run an Action from the Acrobat Professional application when creating a PDF, but you can't ascribe multiple passwords on a per-document basis, only set the same password for all this way.

- There's a JavaScript interface in the main application which can be initiated from an Action. It doesn't seem to expose simple password encryption. 

- There's no command-line argument you can provide to the main application whereby you could specify the necesarry options to encrypt and provide a password.

- If you reference 'AdobePDFMakerForOffice' in VBA, you can see there is an object under ISettings called 'SecuritySettings' but I believe use of this interface is not documented or supported by Adobe.

Is there an easy way of automatically feeding a password to Acrobat at document creation? Am I missing something very obvious? Acrobat definitely produces the best looking PDFs, but we need a bulletproof 100% solution if we're going to meet the high per-seat cost of subscription.