diff --git a/korektury/admin.py b/korektury/admin.py
index 7e74cf27..25b49e4e 100644
--- a/korektury/admin.py
+++ b/korektury/admin.py
@@ -5,7 +5,14 @@ from korektury.models import KorekturovanePDF
 
 # Register your models here.
 class KorekturovanePDFAdmin(VersionAdmin):
+
     readonly_fields = ['cas', 'stran']
+
+    def get_readonly_fields(self, request, obj=None):
+        if obj:
+            return self.readonly_fields + ['pdf']
+        return self.readonly_fields
+
     fieldsets = [
             (None,
                 {'fields':