Add explicit permissions to workflow for security

Co-authored-by: hifly81 <[email protected]>

Author: Copilot

.github/workflows/generate-pdfs-on-release.yml

@@ -7,6 +7,8 @@ on:
 jobs:
   generate-pdfs:
     runs-on: ubuntu-latest
+    permissions:
+      contents: write
 
     steps:
       - name: Checkout repository