If you reach the edge of a flat earth what would happen?

Well being hypothetical, there can only be hypothetical answers.

• You would not exist in a flat Earth - so you couldn't ask this question.
• No flat astronomical objects exist - so you couldn't ask this question.
• Gravity would be messed up - so you couldn't ask this question

Basically - this question cannot be answered as there is no answer, but if you want to believe Pirates of the Caribbean or Terry Pratchett, then you would fall of it - but then you have to ask, where would you fall to, and what is pulling you, and if that object is pulling "you" why has the Earth not succumbed to the same pull?