If a datasheet specifies load capacitance is this quoted per output pin or a total for all pins
It will be the maximum load capacitance for a single output (i.e. per pin). Notice how the diagram specifies "from output under test".



The capacitance is an important consideration in terms of maximum output frequency, which is governed by the time constant of the capacitance coupled with the resistance of the CMOS totem pole.

You shouldn't have an issue driving a 10pF load on all the outputs. CMOS inputs are typically higher capacitance than something like TTL, so the drivers are designed to cope with the higher capacitive load in order to be able to drive a reasonable number of inputs from the same output.