Contrary to what you might expect, merging PDFs is easier on your iPhone than on your Mac. On the desktop, you first need to open both PDFs in the Preview app, and then work out how to combine the two of them. On the iPhone or iPad, you can select your PDFs in the Files app (or in the Mail app, or anywhere else you find them), and use a quick shortcut to combine and save them in one go.
It’s instant, foolproof, and Just Works™. Let’s see just how easy it is to merge PDFs on iOS.