Answer
There's no direct framework support for merging two separately-generated report outputs into a single PDF — the built-in mechanism only supports inserting static PDF pages before, in the middle of, or after a single report's own generation, not combining two independently generated reports together. To actually merge two report outputs, you'd need a customization that fetches both generated PDFs after they're created and merges them programmatically (for example, using a PDF-manipulation library like iText) before emailing the combined result — sending the two reports as separate attachments in the same email is the simplest fallback if a custom merge isn't worth building.