AxAcroPdf - choose between Acrobat Reader or Pro

My customer has Adobe Acrobat Pro (DC) installed in a Citrix (multiuser) environment. A few of their staff have licenses to use Adobe Pro. The other staff use Acrobat Reader DC. However the firm is concerned that they might be breaching the licensing agreement, because when they preview a pdf in Windows Explorer or through an application with AxAcroPdf (the Acrobat Reader ActiveX control in our C# application), then they see the Pro previewer not the Reader previewer. They have tried this with Acrobat Reader XI and DC, same result. It appears that the interop chooses what viewer to use and there is no programmatic control over this choice?