I don't think capital markets relied on the printing press. The Hanseatic league, arguably the first free-trade organisation, was established well before Gutenberg built his press (1150 vs 1450 AD, roughly). Do you have a reference for that? I'm curious to explore it.
If you're referring to the availability of paper money, bank notes were already used in the 7th century AD in China and introduced in Europe by Marco Polo in the 13th century [1], and before that the Knights Templar issued hand-written notes to the same effect.
"New vehicles of credit were imported from Italy, where double-entry book-keeping was invented in 1492, and outpaced the Hansa economy, in which silver coins changed hands rather than bills of exchange."
Bond markets and insurance instruments arose to manage risk in the slave trade.
The relevance of the printing press is only that printed forms were required for conducting commerce between parties that were introduced at arms length i.e. from outside networks of direct personal trust (one or two degrees of separation i.e. someone trusted could vouch for an associate to introduce that associate to a capital merchant, who could document the arrangement with a "hand-written note", with the full knowledge that he had the means to extract revenge in the breach because the parties were known to each other).
With printed forms, the numerous detailed requirements stipulating the terms of guarantee could be mass produced in advance, thus enabling strangers to circumvent the need for personal assurances so they could operate in free and open markets, thus greatly expanding the pool of financiers, entrepreneurs, traders and customers.
See
How the shadow of slavery still hangs over global finance
This long article on the slave trade provides broad and detailed historical context for the evolution of the financial industry, without directly treating finance in depth.
If you're referring to the availability of paper money, bank notes were already used in the 7th century AD in China and introduced in Europe by Marco Polo in the 13th century [1], and before that the Knights Templar issued hand-written notes to the same effect.
[1] https://en.wikipedia.org/wiki/Banknote#European_explorers_an...