What exactly is the problem that needs solution? If you want to keep the hinting information, do not expand the font to outlines. If you want a very specific pixel rendering, do not use outlines. But if you want to keep it scalable and keep outlines, you will have to live with the fact that outline rendering will always vary in different output channels, and there is nothing you can do about it from within the font. Two different PDF renderers will deliver different pixel images.