class Prawn::Table::Cells

table.cells.style { |cell| cell.border_width += 12 }

This allows you to set more complicated properties:
You can also pass a block, which will be called for each cell in turn.

table.cells.border_width = 2
table.cells.padding = 0

is the same as:

table.cells.style(:padding => 0, :border_width => 2)

Supports setting multiple properties at once.

def style(options={}, &block)
  each do |cell|
    next if cell.is_a?(Cell::SpanDummy)
    cell.style(options, &block)
  end
end