Purge existing PDFs first so that old names get removed.

tasks/general/acct_mgmt/users.yml

@@ -849,6 +849,7 @@
     function_ebook_convert: |
       # Regenerate all eBook projects at once.
       function ebook-convert {
+        find ~/Code/ebook-* -name "*.pdf" -print -delete
         find ~/Code/ebook-* -name convert.sh -print -exec bash "{}" \;
       }
       alias ebooks="ebook-convert"