In the present paper, the performance of non-orthogonal multiple access (NOMA) in a downlink multipath multi-user Visible Light Communication (VLC) system has been evaluated w.r.t bit-error rate (BER), sum rate & outage probability. The results show that the sum rate and BER performance improve with the increase in semi-angle of the LED using both Line-of-sight (LOS) and LOS plus first reflection (L-R1) signals. The simulation results display that there is optimal value of at which minimum BER is achieved. However, the optimal angle of semi-angle varies with the number of users and order of reflection of signal. In case of two-user system with LOS signal, the optimal angle is and for user-1 & user-2 respectively, whereas, for three-user system the optimal angle is for user-1 and it is for each user-2 and user-3. The BER simulation results for L-R1 signal reveal that the successive interference cancellation (SIC) efficiently decodes the signal for two-user system with optimum performance at equals to but as the number of users increases to three, it fails to decode the signal. The results of sum rate vs. offset using LOS signal show that sum rate for two-user system monotonically increases & then decreases with the increase in semi-angle. The optimal angle is for the maximum sum rate which also supports the BER results. The effect of shadowing (blocked LOS signal) shows that the sum rate is zero for lower values of semi-angle of LED. Finally, the outage probability against target rate of far user confirms the key finding results of shadowing.