Diode "stacks"
It is not normally recommended that diodes be operated in parallel because each diode turns on at a slightly different forward voltage meaning that one diode may end up taking the brunt of the load. Series-connected rectifiers are common, especially in high-voltage circuits. The ARRL Radio Amateurs Handbook, especially the older ones from the 1960's and 1970's have excellent examples of these in their transmitter and linear ampifier power supplies. Usually, each diode is in parallel with a small (0.01µF) ceramic capacitor and a high-value (100K-1M ohm) resistor. The resistor equalizes the reverse voltage across the diodes so that one that has a higher reverse resistance isn't overstressed and the caps serve to bypass transients that could kill the rectifier.
The voltage rating of the series rectifier stack will be the sum of the rating of the individual diodes (the diodes should be identical!) and the current rating is that of an individual diode.
Dean