The channel flight time (delay) of the interconnect is roughly 1 ns per 15 cm (6 in) of FR-4 stripline (the propagation velocity depends on the dielectric and the geometry). Reflections of previous pulses at impedance mismatches die down after a few bounces up and down the line (i.e. on the order of the flight time). At low bit rates, the echoes die down on their own, and by midpulse, they are not a concern. Impedance matching is neither necessary nor desirable. There are many circuit board types other than FR-4, but usually they are more costly to manufacture.
As far I know, Digital signal bandwidth is function of it's rise and fall time. Hence, Reflected power will dependent upon rise and fall time of the signal, not on bit rate of the signal. However, in the above paragraph, it is mentioned that for low bit rate signal reflected power won't effect the original signal. I am not able to understand the above statement. Can someone help me?