Append instead of replace

sign/pdfvisualsignature.go

@@ -0,0 +1,44 @@
+package sign
+
+import (
+	"errors"
+	"strconv"
+)
+
+func (context *SignContext) createVisualSignature() (visual_signature string, err error) {
+	visual_signature = strconv.Itoa(int(context.VisualSignData.ObjectId)) + " 0 obj\n"
+	visual_signature += "<< /Type /Annot"
+	visual_signature += " /Subtype /Widget"
+	visual_signature += " /Rect [0 0 0 0]"
+
+	root := context.PDFReader.Trailer().Key("Root")
+	root_keys := root.Keys()
+	found_pages := false
+	for _, key := range root_keys {
+		if key == "Pages" {
+			found_pages = true
+			break
+		}
+	}
+
+	if !found_pages {
+		return "", errors.New("Didn't find pages in PDF trailer Root.")
+	}
+
+	rootPtr := root.GetPtr()
+	context.CatalogData.RootString = strconv.Itoa(int(rootPtr.GetID())) + " " + strconv.Itoa(int(rootPtr.GetGen())) + " R"
+
+	page := root.Key("Pages").Key("Kids").Index(0).GetPtr()
+	visual_signature += " /P " + strconv.Itoa(int(page.GetID())) + " " + strconv.Itoa(int(page.GetGen())) + " R"
+
+	visual_signature += " /F 4"
+	visual_signature += " /FT /Sig"
+	visual_signature += " /T " + pdfString("Signature")
+	visual_signature += " /Ff 0"
+	visual_signature += " /V " + strconv.Itoa(int(context.SignData.ObjectId)) + " 0 R"
+
+	visual_signature += " >>"
+	visual_signature += "\nendobj\n"
+
+	return visual_signature, nil
+}