diff --git a/.github/workflows/draft-pdf.yml b/.github/workflows/draft-pdf.yml
index d8a1267..6172957 100644
--- a/.github/workflows/draft-pdf.yml
+++ b/.github/workflows/draft-pdf.yml
@@ -1,6 +1,9 @@
 name: Build paper PDF
 
-on: [push]
+on:
+  pull_request:
+    branches:
+      - paper
 
 jobs:
   paper: