public DocumentEncryption(PDDocument doc) 
{
        pdDocument = doc;
        document = doc.getDocument();
}

Constructor.

Parameters:

doc - The document to decrypt.

 public DocumentEncryption(COSDocument doc) 
{
        pdDocument = new PDDocument( doc );
        document = doc;
}

Constructor.

Parameters:

doc - The document to decrypt.

 public  void decrypt(Object obj,
    long objNum,
    long genNum) throws CryptographyException, IOException 
{
        if( !objects.contains( obj ) )
        {
            objects.add( obj );
            if( obj instanceof COSString )
            {
                decryptString( (COSString)obj, objNum, genNum );
            }
            else if( obj instanceof COSStream )
            {
                decryptStream( (COSStream)obj, objNum, genNum );
            }
            else if( obj instanceof COSDictionary )
            {
                decryptDictionary( (COSDictionary)obj, objNum, genNum );
            }
            else if( obj instanceof COSArray )
            {
                decryptArray( (COSArray)obj, objNum, genNum );
            }
        }
}

This will dispatch to the correct method.

 public  void decryptDocument(String password) throws CryptographyException, IOException, InvalidPasswordException 
{
        if( password == null )
        {
            password = "";
        }
        PDStandardEncryption encParameters = (PDStandardEncryption)pdDocument.getEncryptionDictionary();
        int permissions = encParameters.getPermissions();
        int revision = encParameters.getRevision();
        int length = encParameters.getLength()/8;
        COSString id = (COSString)document.getDocumentID().getObject( 0 );
        byte[] u = encParameters.getUserKey();
        byte[] o = encParameters.getOwnerKey();
        boolean isUserPassword =
            encryption.isUserPassword( password.getBytes(), u,
                o, permissions, id.getBytes(), revision, length );
        boolean isOwnerPassword =
            encryption.isOwnerPassword( password.getBytes(), u,
                o, permissions, id.getBytes(), revision, length );
        if( isUserPassword )
        {
            encryptionKey =
                encryption.computeEncryptedKey(
                    password.getBytes(), o,
                    permissions, id.getBytes(), revision, length );
        }
        else if( isOwnerPassword )
        {
            byte[] computedUserPassword =
                encryption.getUserPassword(
                    password.getBytes(),
                    o,
                    revision,
                    length );
            encryptionKey =
                encryption.computeEncryptedKey(
                    computedUserPassword, o,
                    permissions, id.getBytes(), revision, length );
        }
        else
        {
            throw new InvalidPasswordException( "Error: The supplied password does not match " +
                                                "either the owner or user password in the document." );
        }
        COSDictionary trailer = document.getTrailer();
        COSArray fields = (COSArray)trailer.getObjectFromPath( "Root/AcroForm/Fields" );
        //We need to collect all the signature dictionaries, for some
        //reason the 'Contents' entry of signatures is not really encrypted
        if( fields != null )
        {
            for( int i=0; i< fields.size(); i++ )
            {
                COSDictionary field = (COSDictionary)fields.getObject( i );
                addDictionaryAndSubDictionary( potentialSignatures, field );
            }
        }
        List allObjects = document.getObjects();
        Iterator objectIter = allObjects.iterator();
        while( objectIter.hasNext() )
        {
            decryptObject( (COSObject)objectIter.next() );
        }
        document.setEncryptionDictionary( null );
}

This will decrypt the document.

 public  void initForEncryption() throws CryptographyException, IOException 
{
        String ownerPassword = pdDocument.getOwnerPasswordForEncryption();
        String userPassword = pdDocument.getUserPasswordForEncryption();
        if( ownerPassword == null )
        {
            ownerPassword = "";
        }
        if( userPassword == null )
        {
            userPassword = "";
        }
        PDStandardEncryption encParameters = (PDStandardEncryption)pdDocument.getEncryptionDictionary();
        int permissionInt = encParameters.getPermissions();
        int revision = encParameters.getRevision();
        int length = encParameters.getLength()/8;
        COSArray idArray = document.getDocumentID();
        //check if the document has an id yet.  If it does not then
        //generate one
        if( idArray == null || idArray.size() <  2 )
        {
            idArray = new COSArray();
            try
            {
                MessageDigest md = MessageDigest.getInstance( "MD5" );
                BigInteger time = BigInteger.valueOf( System.currentTimeMillis() );
                md.update( time.toByteArray() );
                md.update( ownerPassword.getBytes() );
                md.update( userPassword.getBytes() );
                md.update( document.toString().getBytes() );
                byte[] id = md.digest( this.toString().getBytes() );
                COSString idString = new COSString();
                idString.append( id );
                idArray.add( idString );
                idArray.add( idString );
                document.setDocumentID( idArray );
            }
            catch( NoSuchAlgorithmException e )
            {
                throw new CryptographyException( e );
            }
        }
        COSString id = (COSString)idArray.getObject( 0 );
        encryption = new PDFEncryption();
        byte[] o = encryption.computeOwnerPassword(
            ownerPassword.getBytes("ISO-8859-1"),
            userPassword.getBytes("ISO-8859-1"), revision, length);
        byte[] u = encryption.computeUserPassword(
            userPassword.getBytes("ISO-8859-1"),
            o, permissionInt, id.getBytes(), revision, length);
        encryptionKey = encryption.computeEncryptedKey(
            userPassword.getBytes("ISO-8859-1"), o, permissionInt, id.getBytes(), revision, length);
        encParameters.setOwnerKey( o );
        encParameters.setUserKey( u );
        document.setEncryptionDictionary( encParameters.getCOSDictionary() );
}

This will encrypt the given document, given the owner password and user password. The encryption method used is the standard filter.