Default: warning
In Inference Works → Order invoices, configure When the invoice is missing.
By default, completing an order without a PDF produces a warning. The status still changes, the email is sent without the attachment, and an admin notice and order note are recorded. A warning does not mean that the email was stopped.
Optional: block manual changes
Choose blocking mode if a manual change to Completed should be reverted until a PDF has been uploaded. Save the setting, upload the finished invoice to the order and retry the status change.
Automatic changes — checkout, REST, WP-CLI and cron — always use warning mode, even when blocking is selected. This prevents missing PDFs from holding up payments or order automation.
Test the setting
- On a test order without a PDF, manually change the status to Completed.
- Check the notice, order note and resulting status against the selected mode.
- Upload the PDF and retry. The selected email should contain the attachment.