1/ I sign a file using this method
public static void signByPdfbox(
throws IOException, UnrecoverableKeyException, KeyStoreException, NoSuchAlgorithmException, COSVisitorException, SignatureException
2/ I resign the same file using the same method and in acrobat reader I have this error : SignDict/Contents illegal data
I have googelized it, and I found only old topics for iText lib.
I have tried the same with iText 5.X, and double signatures works