I have a decent amount of experience creating epub files and converting them to .mobi using Kindlegen or Amazon Kindle Previewer 3 for self publishing on KDP. I'm looking to add the "real page numbers" feature to a book (this is useful in textbooks because people still tend to like to reference page numbers when citing). Amazon rolled out this feature in 2011, but I can find no current or relevant information for how to do this, other than general guidance that Kindle references an embedded ".apnx" file to identify the page numbers. Can anyone point me in the right direction?
Note that the official Amazon tools won't generate APNX files. However, KindleUnpack can generate them from a mobi file generated by KindleGen.
You could also generate KFX files with the unofficial KFX plugin. When transferred to an eInk device, the firmware will automatically generate the APNX files.