FPDI_Protection_128 makes use of some predefined constants.
SETAPDF_ENC_RC4_40 (integer) = 0
Standard encryption with 40-bits.
SETAPDF_ENC_RC4_128 (integer) = 1
Standard encryption with 128-bits.
SETAPDF_ENC_AES (integer) = 2
AES (Advanced Encryption Standard) encryption with 128-bits.