diff --git a/README.md b/README.md
index ed39139..e3dea1e 100644
--- a/README.md
+++ b/README.md
@@ -79,4 +79,9 @@ val output = File("Zugferd.pdf")
 val creator = EInvoiceCreator()
 
 creator.combinePdfAndInvoiceXml(invoice, existingPdf, output)
+
+// or if you already have the invoice XML:
+val invoiceXml: String = "..." // e.g. creator.createZugferdXml(invoice)
+
+creator.combinePdfAndInvoiceXml(invoiceXml, existingPdf, output)
 ```
\ No newline at end of file
diff --git a/e-invoicing-domain/src/test/kotlin/net/codinux/invoicing/Demonstration.kt b/e-invoicing-domain/src/test/kotlin/net/codinux/invoicing/Demonstration.kt
index 69a3424..d0c4aed 100644
--- a/e-invoicing-domain/src/test/kotlin/net/codinux/invoicing/Demonstration.kt
+++ b/e-invoicing-domain/src/test/kotlin/net/codinux/invoicing/Demonstration.kt
@@ -70,6 +70,11 @@ class Demonstration {
         val creator = EInvoiceCreator()
 
         creator.combinePdfAndInvoiceXml(invoice, existingPdf, output)
+
+        // or if you already have the invoice XML:
+        val invoiceXml: String = "..." // e.g. creator.createZugferdXml(invoice)
+
+        creator.combinePdfAndInvoiceXml(invoiceXml, existingPdf, output)
     }