Hi Carl. Depending on which face has to be improved, you might want to consider playing with the Levels however, it will only help emphasize areas that are not completely white. PSP can use the variations of colors that are faint, but any pixel that is pure white or pure black would not be useful. If you have some areas where it has some grey, it might work.
Also, it will help if you have the highest resolution possible (if you can scan or rescan the original) as it would give more pixels to retrieve details.