FrankyBox

I've opened the Help file from within Affinity Photo (PC), then clicked on any topic while holding the Shift key, got online, then saved the page form my browser onto my computer, bingo! Got the complete file saved! Hope that helps.

For PC users: I simply downloaded the complete Help page all in one go. From Affinity Photo click Help (F1), then click on any topic holding the Shift key, the file opens online, click on your browser's Save/Save Page button to save it on your computer and that's it!