AES-256 in Galois/Counter Mode with a random 256-bit file key: V 6, revision 7, crypt filter method AESV4. PDF 2.0
with the ISO/TS 32003 extension, which the save declares in the catalog's Extensions (ISO_, level 32003). Every
string and stream carries its own authentication tag; few readers support it yet.
Aes256Gcm = 3
ISO/TS 32003 §5.1 (Tables 2 to 4: V 6, R 7, AESV4; the password algorithms of revision 6) and §5.2 (AES-GCM
with the file key, a 12-byte IV per string or stream, a 16-byte tag, no additional authenticated data).