I am encrypting my PDF Files using "enrypt all document content & require a password to open the document" feature.
Which one is more secured and how secured is it?
i) Encrypted Pdf files using the above feature
ii) Unencrypted pdf files saved in a 256-bit AES encrypted disk image on a mac
What is the most secured option for documents?
What are you trying to secure against, exactly? PDFs can be secured using different strengths (e.g., 40-bit RC4, 128-bit RC4 and AES, AES-256), so it depends on which you're using. Brute force attacks depend on the password strength and other types of attacks depend on how securely the passwords are recorded and stored. There are a number of variables to consider.