Aloha Ron,
A replacement of fluid is a good start, particularly if it is three year old or older or you have no idea of its age. All of the DOT 3 and 4 fluids will absorb moisture over time which will reduce the boiling point and deteriorate brake performance. I am assuming that you have checked and there are no apparent leaks. Usually, if air is in the system, pumping the brakes increases pedal stiffness as the air is compressed. Bleeding removes this air to give you a firm pedal on the first stroke. If the pedal moves closer to the floor board on successive strokes, it may be that either the resevoir is low or the master cylinder is not holding the pressure. If the fluid level is good, the situation most likely calls for either a replacement or rebuild of the master cylinder.
Safety Fast,
Dave