extract-file-from-pdf.rb

reader = PDF::Reader.new('some.pdf')
filename = "transactions.csv" # obtain this from the XFA in the pdf
page = reader.pages.first
attachment_name_reference = page.objects.find do |k, v|
  page.objects.obj_type(k) == :Hash && v[:Type] == :Filespec && v[:UF] == filename }.first
end
attachment_content_reference = page.objects[attachment_name_reference][:EF][:F]
attachment_content = page.objects[attachment_content_reference].unfiltered_data