据说rpdf2txt库可以解析
require 'rpdf2txt/parser'
require 'rpdf2txt/default_handler'
parser = Rpdf2txt:

arser.new(File.read('filename.pdf'))
output = File.open('a.txt', 'w')
handler = Rpdf2txt::SimpleHandler.new(output)
parser.extract_text(handler)
但'a.txt'中是空的,有谁能解决这个问题?