That actually seems to be just what I envisioned. I notice that the PDF files get added as data to a custom PDF viewer which gets in the way of between the view

That actually seems to be just what I envisioned. I notice that the PDF files get added as data to a custom PDF viewer which gets in the way of between the viewer and the system. This is pretty much how I would have implemented it except that the error messages are not handled correctly. It stops you printing by making the viewer think that the printer is not connected, the error message is misleading in that it claims that the printer is not available when it really means that you are not allowed to print the document. However without having one of those to hand I don't know how hackable they are. I am mildly curious as to how this is implemented and wouldn't mind trying to hack one. But I note that they don't publish their prices so I suspect that it is beyond my budget.