libharu：HPDFDoc::HPDF_PAGE_NUM_STYLE_UPPER_LETTERS

#!/usr/bin/env ruby

require "hpdf"

pdf  = HPDFDoc.new
pdf.add_page_label(0, HPDFDoc::HPDF_PAGE_NUM_STYLE_UPPER_LETTERS, 1, "")

30.times do
  page = pdf.add_page
end

pdf.save_to_file(File.basename($0, ".rb") + ".pdf")

「Z」の後は「AA」「BB」〜と続くようだ