Fix Signature Flags

@@ -11,6 +11,7 @@
 - Add PdfColor.flatten
 - Add A6 page format
 - Apply Flutter 2.2 format
+- Fix Signature Flags
 
 ## 3.3.0
 

@@ -69,7 +69,7 @@ class PdfSignature extends PdfObjectDict {
   int get flagsValue => flags.isEmpty
       ? 0
       : flags
-          .map<int>((PdfSigFlags e) => 1 >> e.index)
+          .map<int>((PdfSigFlags e) => 1 << e.index)
           .reduce((int a, int b) => a | b);
 
   final crl = <PdfObjectStream>[];