Dick Cole (left) and Bert Biscoe at the launch
They are hoping to win support at Westminster and in Europe with a simultaneous launch of the leaflet in London, Brussels and in Cornwall.
The Cornish Constitutional Convention, which is organising the devolution campaign, is pressing for a referendum on the issue in the next 18 months.
Supporters claim a Cornish parliament would enhance the self-confidence of the region.
Wide powers
The publication sets out for the first time what powers the assembly would have, how delegates would be elected and how it would operate with central and local government.
The Devolution for One and All pamphlet outlines an elected assembly of 40 or 50 members and a cabinet of seven or eight.
Their powers will include looking after health, employment, fisheries, education, arts, sport and culture.
Central government would retain control of key functions, such as home and foreign affairs, defence and national taxation.
The vice chairman of the convention, Councillor Dick Cole, said: "The Cornish assembly is not about an extra tier of government.
"At the present time we have quangos stretching back to Bristol.
"They would be brought within democratic control and there will be a tier of local government within Cornwall, underneath the assembly, delivering local services.
"It is about local government, better government and about government in Cornwall for Cornwall."
County councillor Alistair Quinnell said: "This is not about separatism, it is not about isolation.
"It is about Cornwall playing as the equal partner with others and being able to regenerate that self-confidence that will give us a sense of get-up-and-go."
A recent petition calling for a referendum for a Cornish assembly was signed by 50,000 people from the county.