diff --git a/models/sign_document.py b/models/sign_document.py
index 70eea81..9abaf22 100644
--- a/models/sign_document.py
+++ b/models/sign_document.py
@@ -30,6 +30,7 @@ class SignDocument(models.Model):
             return base_output
 
         try:
+            base_output.seek(0)  # IMPORTANT: Reset stream position to start
             base_pdf = PdfFileReader(base_output, strict=False)
         except (ValueError, PdfReadError):
             return base_output