Answer
Report PDF generation is asynchronous, so the generated PDF genuinely isn't available yet within the same PL/SQL block that triggered it — instead, hook the standard PDF_REPORT_CREATED event, which fires once the PDF generation has actually completed, and build your email-sending logic (using command_sys.mail with the generated report as the attachment) inside that event instead of trying to send immediately after triggering generation. Since PDF_REPORT_CREATED fires once per individual report, if you need several reports combined into a single email, use a Report Rule with the 'Route to Connect' action type to save each report's PDF to a known path on the application server first, then separately trigger one email afterward (from a custom menu PL/SQL action or a background job) that attaches each of the saved report files by their file paths, rather than relying on PDF_REPORT_CREATED's one-event-per-report firing pattern to build a combined email.