Affinity Publisher Bug: The attached FontTest.afpub has 8 different fonts -- both serif and sans serif. When exporting to PDF (Export Settings: PDF (for web), 72 dpi, preview...), and the PDF sent via iTunes to with the iDevice's Books application or Acrobat application, font failure happens.
We tested an iPhone 7 and 7+ (OS 12.4) and an older iPad (OS 10.3.4). What happens is that the letters ff, fi and others starting with f will not print using several fonts: Verdana, Arial, Georgia, Times New Roman.
All works correctly using Garamond, Calibri, Myriad Pro, Adobe Caslon Pro. (We didn't test additional fonts.)
All looks correct when the PDF is viewed on a PC, but not on our iPhones or iPads.
FontTest.afpub