Serial letter better file name

process/buildSerialLetter_serverProcess/process.js

+import("Document_lib");
 import("system.text");
 import("system.translate");
 import("Binary_lib");
@@ -13,11 +14,10 @@ var letterId = vars.get("$local.serialLetterId");
 var recipientIds = JSON.parse(vars.get("$local.recipientIds"));
 
 var document = SerialLetterUtils.buildSerialLetter(letterId, recipientIds)
- 
-//if (document)
-//    neon.download(document, template.filename);
 
-SingleBinaryUtils.set("SERIALLETTER", "SERIALLETTERFILE", letterId, document.content, document.filename, "");
+var filename = document.title + "." + DocumentUtil.getFileExtensionFromUpload(document.filename);
+
+SingleBinaryUtils.set("SERIALLETTER", "SERIALLETTERFILE", letterId, document.content, filename, "");
 
 var message = translate.text("Download ready");
 var description = translate.withArguments("Serial letter \"%0\" can now be downloaded", [document.title]);