Add a secure signature to a pdf file.
gem install firma
require "firma"
Firma.is_signed?("my_file.pdf")
require "firma"
Firma.sign("my_file.pdf",
key: "key.pem",
passphrase: "passphrase",
certificate: "key.crt"
)
require "firma"
keys = Firma.generate_keys("passphrase")
Firma.sign("my_file.pdf",
key: keys.fetch(:key),
passphrase: "passphrase",
certificate: keys.fetch(:certificate)
)