Pfft! What a waste of time. You can natively get a PDF of any image just by going into the print dialog and expanding out the thumbnail image...that is a PDF.

Looking at the past posts from this user makes me corcerned for the iOS app ecosystem, it truly seems orwellian, I guess I will keep "sideloading" from trusted sources like fdroid

$5 for one very specific and rudimentary feature. iOS life is so god damn weird.