Specifies standard security algorithms.

Values:

IG_PDF_STD_SECURITY_METHOD_RC4_V2	2	RC4 algorithm for encryption.
IG_PDF_STD_SECURITY_METHOD_AES_V1	5	AES algorithm for encryption with a zero initialized iv.
IG_PDF_STD_SECURITY_METHOD_AES_V2	6	AES algorithm for encryption with a random initialized iv.
IG_PDF_STD_SECURITY_METHOD_AES_V3	7	AES algorithm for encryption with a 4 byte random iv.