PDF Studio 9 and above: Support for opening and encrypting PDFs with the latest algorithm AES 256 algorithm (R=6). This algorithm was defined in the latest PDF specifications (PDF 2.0) and is compatible with Acrobat X and later. The new algorithm is used when applying new signatures but the “old” algorithm (R=5) is still verified in existing signatures for backward compatibility with Adobe Acrobat 9.

PDF Studio 7, 8: Support for opening as well as encrypting PDF documents with 256-bit AES encryption, compatible with Acrobat 9.

PDF Studio 6: Support for opening documents encrypted with AES 256 encryption but no support for encrypting documents using AES 256 encryption.