This shows the logic needed to test for two the different PDF encryption modes. It is written in C#, and has been tested with version 1.2.1 of PDFBox, cross-compiled to .net using IKVM (http://www.ikvm.net/).

PDF Encryption test for .net

Console.WriteLine("Document encrypted = {0}", document.isEncrypted().ToString());
// Can it be opened?
bool isOpenable = true;
if (document.isEncrypted())
{
    DecryptionMaterial decryptionMaterial = new StandardDecryptionMaterial("");
    try
    {
        document.openProtection(decryptionMaterial);
        AccessPermission ap = document.getCurrentAccessPermission();
        if (ap.isOwnerPermission())
        {
        Console.WriteLine("You have owner rights.");
        }
        else
        {
        Console.WriteLine("You do not have owner rights.");
        }
    }
    catch (CryptographyException e)
    {
        Console.WriteLine("Cannot open document. :: {0}",e.getMessage());
        isOpenable = false;
    }
}
Console.WriteLine("Document openable = {0}", isOpenable);
// Detailed rights:
if (isOpenable)
{
    Console.WriteLine("Rights: canExtractContent = {0}", document.getCurrentAccessPermission().canExtractContent().ToString());
}