The method is like this, call directly.
The public static void symbol (string before Pdfpath, string after Pdfpath, pngpath string) throws an exception {
//KeyStore ks = KeyStore . getinstance(" pkcs 12 ")；
//ks . load(new file inputstream(" demo . p 12 ")，" 123456 "。 toCharArray())； // 123456 is the private key password.
//String alias =(String)ks . aliases()。 next element()；
//privatekeykey = (privatekey) ks.getkey (alias, "123456"). toCharArray())；
//certificate [] chain = ks.get certificate chain (alias);
Log.d("pdfd "，" do- 1 ")；
pdf reader reader = new pdf reader(before pdf path)； //source file
Log.d("pdfd "，" do- 1-0 1 ")；
file output stream fout = new file output stream(afterpdf path)；
Log.d("pdfd "，" do- 1- 1 ")；
PdfStamper STP = PdfStamper . create signature(reader，fout，' \ 0 ')；
PdfSignatureAppearance sap = STP . getsignaturerenance()；
//sap . set crypto(key，chain，null，PdfSignatureAppearance。 VERISIGN _ SIGNED)；
Log.d("pdfd "，" do-2 ")；
sap . set reason(" ")；
sap . set location(" ")；
sap . set contact("/")；
image image = image . getinstance(png path)； //Use transparent pictures in png format.
Log.d("pdfd "，" do-3 ")；
sap . setsignaturegraphic(image)；
sap . seta cro 6 layers(true)；
sap . setrenderingmode(rendering mode。 Graphic);
Sap.setVisibleSignature (new rectangle (300,600,400,675), 1, null); //300 and 600 are the coordinates corresponding to the X axis and the Y axis.
stp.getWriter()。 setCompressionLevel(5)；
Log.d("pdfd "，" do-4 ")；
If (stp! = null) {
Log.d("pdfd "，" do-4- 1 ")；
STP . close()；
Log.d("pdfd "，" do-4-2 ")；
}
Log.d("pdfd "，" do-5 ")；
If (fout! = null) {
fout . close()；
}
Log.d("pdfd "，" do-6 ")；
If (reader! = null) {
reader . close()；
}
Log.d("pdfd "，" do-7 ")；
}