PDF Gen - Update the Instruction Module

As discussed, the instruction pages for our PDFs will now be provided by other teams as separate PDF files. To ensure compatibility with our PDF generation service, we need to implement a feature as part of the new proof of concept (POC) to append these instruction PDF pages to the bottom of the generated PDF.

**TODOs**

- [ ] Investigate how to append multiple instructions PDF pages to the end of a generated PDF.
- [ ] Implement the functionality to add these instruction pages seamlessly to the bottom of the PDF generated by our service.
- [ ] Verify that the instruction pages are correctly appended and integrated with the generated PDFs.
- [ ] Add/update tests as appropriate

Start by locating the PDF generation service and its proof-of-concept entry point, then investigate how it currently creates generated PDFs and how multiple external instruction PDF pages can be appended. Done means the service accepts the instruction PDFs, appends all their pages to the generated PDF, and includes tests confirming the resulting page order and integration.

Written by the indexing model from the issue text.