Convert signature into human readable (bouncycastle)

I want to sign a file I read in with JFileChooser. But when I print it to the terminal I can only read questonmarks and other not human readable characters. My code to sign is:

public static void sign() throws Exception{
    byte[] file = fileChooser();

    store = KeyStore.getInstance(storeType);
    FileInputStream in = new FileInputStream(new File(storePath));
    store.load(in, storePassword);
    in.close();

    Key priv = store.getKey("test", storePassword);
    System.out.println(priv.toString() + "priv string");
    X509Certificate cert = (X509Certificate) store.getCertificate("Subject");
    ContentSigner signer = new JcaContentSignerBuilder("SHA512withRSA").build((RSAPrivateKey) priv);        

    //Sign Data
    Signature signature = Signature.getInstance("SHA512WithRSA");
    signature.initSign((RSAPrivateKey) priv);
    signature.update(file);

    //Build cms
    CMSTypedData data = new CMSProcessableByteArray(signature.sign()); 
    CMSSignedDataGenerator gen = new CMSSignedDataGenerator();

    gen.addSignerInfoGenerator(
            new JcaSignerInfoGeneratorBuilder(
                    new JcaDigestCalculatorProviderBuilder().build())
                    .build(signer, cert));

    //Get signed data
    CMSSignedData sigData = gen.generate(data, false);

    byte[] sig = (byte[]) sigData.getSignedContent().getContent();
    sig.toString();
    String content = new String(sig);
    System.out.println("Signed content: " + content + "\n");
}

How can I format the signature to human readable?