diff --git a/laws-modules/src/main/java/com/jero/modules/laws/enterprise/util/WaterMarkUtil.java b/laws-modules/src/main/java/com/jero/modules/laws/enterprise/util/WaterMarkUtil.java
index 8f6b44ce..a9e78475 100644
--- a/laws-modules/src/main/java/com/jero/modules/laws/enterprise/util/WaterMarkUtil.java
+++ b/laws-modules/src/main/java/com/jero/modules/laws/enterprise/util/WaterMarkUtil.java
@@ -41,7 +41,7 @@ public class WaterMarkUtil {
         return userName + " " + formattedDate;
     }
 
-    public InputStream addWatermarkToPdf(InputStream inputStream) throws IOException {
+    public synchronized InputStream addWatermarkToPdf(InputStream inputStream) throws IOException {
         String watermarkText = getWaterMarkConfig();
         PDDocument document = PDDocument.load(inputStream);