How to enable an API user access to removeDocument method?

Hi - I need to allow the API user to delete documents via the removeDocument method. When I call that method with a documentKey, I get an API error:

[removeDocumentResult] => stdClass Object

        (

            [errorCode] => INVALID_API_KEY

            [errorMessage] => You do not have permission to execute this API method.

            [success] =>

        )

Nevermind that the error code indicates that the API key is invalid (it isn't - I've been able to send documents through to ADC with that same key), but I don't see anywhere in the User dashboard that would grant the permission to the API user to execute removeDocument.

Any help appreciated - thx