There are two methods of exporting PDFs both out of Apple Photos and Mimeo Photos.
Apple Photos Project PDF Export
This process is used for creating print-ready PDFs to import into our printing site of projects that were created in an Apple Photos Project and have not or cannot be converted to Mimeo Photos.
This PDF allows you to view and print your Apple Photos Project. These file types can be uploaded to our import site.
Find out how here: How do I use the Apple Photo Project Ordering Service
Mimeo Photos PDF Export
This process is used for creating view only PDFs for proofing your project. This PDF will be watermarked and will be emailed to you upon export. This PDF should not be uploaded to the import site as this will print the watermark.
Find out how here: Export Mimeo Photos PDFs