diff --git a/models/sign_document.py b/models/sign_document.py
index 750d6c0..0365271 100644
--- a/models/sign_document.py
+++ b/models/sign_document.py
@@ -33,6 +33,7 @@ class SignDocument(models.Model):
         # 3. Load the base output into PdfFileReader
         # base_output is a BytesIO
         try:
+            base_output.seek(0)  # IMPORTANT: Reset stream position to start
             base_pdf = PdfFileReader(base_output, strict=False)
         except (ValueError, PdfReadError):
             # Should not happen if super succeeded, but safety first