Latest release (March 2025)

public void SignDocument()
{
    string certFilePath = "cert.pfx";
    string sampleFilePath = "sample.pdf";
    string sampleOutputFilePath = "signed.pdf";
    using (Signature.Signature signature = new Signature.Signature(sampleFilePath))
    {
        // initialize digital option with certificate file path
        DigitalSignOptions options = new DigitalSignOptions(certFilePath)
        {
            // certificate password
            Password = "1234567890",
            // digital certificate details
            Reason = "Sign",
            Contact = "JohnSmith",
            Location = "Office1",
            AllPages = true,
            Width = 80,
            Height = 60,
            VerticalAlignment = VerticalAlignment.Bottom,
            HorizontalAlignment = HorizontalAlignment.Right,
            Margin = new Padding() {  Bottom = 10, Right = 10},
            HashAlgorithm = HashAlgorithm.Sha256
        };
        options.CustomSignHash = new CustomDigitalSigner();
        
        signature.Sign(sampleOutputFilePath, options);
    }
}

public class CustomDigitalSigner : ICustomSignHash
{
    public byte[] CustomSignHash(byte[] signableHash, HashAlgorithm hashAlgorithm, SignatureContext signatureContext)
    {
        string inputP12 = "";
        var inputPfxPassword = "1234567890";
        X509Certificate2 signerCert = new X509Certificate2(inputP12, inputPfxPassword, X509KeyStorageFlags.Exportable);
        RSACryptoServiceProvider rsaCSP = new RSACryptoServiceProvider();
        var xmlString = signerCert.PrivateKey.ToXmlString(true);
        rsaCSP.FromXmlString(xmlString);
        byte[] signedData = rsaCSP.SignData(signableHash, hashAlgorithm);
        return signedData;
    }
}