PDF Editing on iOS - image replace?

so on we create ID cards on PC to print from a template, we just edit pdf, change the relevant text and replace the image with a new photo and print,  template keeps everything neat and tidy.

trying to move over to doing it on my iPad, BUT replace image isn’t there? I can replace text, import a new image but not replace? This is important as the template properly masks off the image, so an import wouldn’t work. 

Ive searched to no avail, but found other apps that can replace images, but feel loathed to buy a 3rd party app when the actual adobe app should surely do it?

am I missing something obvious?