itext7 sign pdf with certificate from user's store without "exportable" property

Question

So we have this C# code that uses the itext7 library to sign pdf's:

public static void SignPDFDocument(string src, string dest, string thumbprint)
    {
        GetStoreCertificates("MY", StoreLocation.CurrentUser);
        cert = GetCertificateFromCollection(thumbprint);

        var privateKey = Org.BouncyCastle.Security  //I think this part needs "exportable" cert
            .DotNetUtilities
            .GetKeyPair(cert.GetRSAPrivateKey())
            .Private;

        var boucyCertParsed = new Org.BouncyCastle.X509
            .X509CertificateParser()
            .ReadCertificate(cert.GetRawCertData());

        Org.BouncyCastle.X509
            .X509Certificate[] bouncyCert = { boucyCertParsed };

        PdfReader reader = new PdfReader(src);
        StampingProperties stampProp = new StampingProperties();
        stampProp.PreserveEncryption();
        PdfSigner signer = new PdfSigner(
            reader,
            new FileStream(dest, FileMode.Create),
            stampProp);

        string digestAlgorithm = DigestAlgorithms.SHA256;
        IExternalSignature signature = new PrivateKeySignature(privateKey, digestAlgorithm);

        signer.SignDetached(signature, bouncyCert, null, null, null, 0, CryptoStandard.CADES);

        reader.Close();
    }

The only problem I have with this, is that the user, needs to have the certificate installed and marked as exportable for this to work. Is there any workaround?