PDF::Writer：PDF::SimpleTable#title, #title=

require 'pdf/simpletable'

pdf = PDF::Writer.new

PDF::SimpleTable.new do |tab|
  tab.column_order = %w(col1 col2 col3)

  p tab.title
  tab.title = "TITLE"
  p tab.title

  tab.show_lines    = :all
  tab.show_headings = true

  data = [
    { "col1" => "foo", "col2" => "bar", "col3" => "baz" },
  ]

  tab.data.replace data
  tab.render_on(pdf)
end

pdf.save_as("2008032500.pdf")

で、

nil
"TITLE"