import com.lowagie.text.Rectangle;
import com.lowagie.text.pdf.*;
import java.io.*;
import java.security.*;
import java.util.Enumeration;

public class Main
{

    public Main()
    {
    }

    public static void main(String args[])
    {
        String s = "input.pdf";
        String s1 = "output.pdf";
        String s2 = "cert.pfx";
        try
        {
            for(int i = 0; i < args.length; i++)
            {
                if(args[i].toLowerCase().equals("-in") && args[i + 1] != null)
                    s = args[i + 1];
                if(args[i].toLowerCase().equals("-out") && args[i + 1] != null)
                    s1 = args[i + 1];
                if(args[i].toLowerCase().equals("-pfx") && args[i + 1] != null)
                    s2 = args[i + 1];
            }

        }
        catch(Exception exception)
        {
            System.out.println("Usage: command -in input.pdf -out output.pdf -key key.pfx");
        }
        sign(s, s1, s2);
    }

    public static void sign(String s, String s1, String s2)
    {
        try
        {
            KeyStore keystore = KeyStore.getInstance("pkcs12");
            keystore.load(new FileInputStream(s2), "PASSPHRASE".toCharArray());
            String s3 = (String)keystore.aliases().nextElement();
            PrivateKey privatekey = (PrivateKey)keystore.getKey(s3, "PASSPHRASE".toCharArray());
            java.security.cert.Certificate acertificate[] = keystore.getCertificateChain(s3);
            PdfReader pdfreader = new PdfReader(s);
            FileOutputStream fileoutputstream = new FileOutputStream(s1);
            PdfStamper pdfstamper = PdfStamper.createSignature(pdfreader, fileoutputstream, '\0');
            PdfSignatureAppearance pdfsignatureappearance = pdfstamper.getSignatureAppearance();
            pdfsignatureappearance.setCrypto(privatekey, acertificate, null, PdfSignatureAppearance.WINCER_SIGNED);
            pdfsignatureappearance.setContact("NAME");
            pdfsignatureappearance.setLocation("ORT");
            pdfsignatureappearance.setVisibleSignature(new Rectangle(450F, 60F, 650F, 80F), 1, null);
            pdfsignatureappearance.setExternalDigest(new byte[128], new byte[20], "RSA");
            pdfsignatureappearance.preClose();
            MessageDigest messagedigest = MessageDigest.getInstance("SHA1");
            byte abyte0[] = new byte[8192];
            InputStream inputstream = pdfsignatureappearance.getRangeStream();
            int i;
            while((i = inputstream.read(abyte0)) > 0) 
                messagedigest.update(abyte0, 0, i);
            byte abyte1[] = messagedigest.digest();
            PdfPKCS7 pdfpkcs7 = pdfsignatureappearance.getSigStandard().getSigner();
            Signature signature = Signature.getInstance("SHA1withRSA");
            signature.initSign(privatekey);
            signature.update(abyte1);
            pdfpkcs7.setExternalDigest(signature.sign(), abyte1, "RSA");
            PdfDictionary pdfdictionary = new PdfDictionary();
            pdfdictionary.put(PdfName.CONTENTS, (new PdfString(pdfpkcs7.getEncodedPKCS7())).setHexWriting(true));
            pdfsignatureappearance.close(pdfdictionary);
        }
        catch(Exception exception)
        {
            System.out.println("KeyStoreException aufgetreten.");
            exception.printStackTrace();
        }
    }
}