Thanks for your question, Gerard. We don’t know how many colonists read the Australian Constitution before referendums (vote of the people) were held to decide if the six colonies should federate. However, federation was a topic of much interest and debate in the Australian colonies and was widely reported on in the newspapers.
The papers covered the process of drafting the Constitution, which happened at a series of conventions or meetings attended by representatives from the colonies in the 1890s. Newspapers also published detailed articles explaining the Constitution and some even included the full text of the Constitution. Groups urging a yes or no vote in the referendums held public meetings and produced leaflets to argue their case, and this in turn was reported on by the newspapers.
Given this sort of coverage, most Australians probably had a reasonable knowledge of the Constitution before voting in the referendums. In the event, the people voted overwhelmingly to federate.