(I have already posted this in community, but was directed here. Fortunately there is a "solution" but it is a bit laborsome, at least the first time: see here:
https://community.adobe.com/t5/acrobat-discussions/choose-sheet-size-and-other-properties-when-creating-pdfs-from-jpeg/m-p/14284448#M441904

Suggestion:

Hello,

I think that the possibility to choose sheet size and other properties when creating pdfs from jpeg is missing. It is nice to be able to combine several jpegs to a pdf by the "combine function", but unfortunately, this creates huge sheets of the jpegs as opposed to the regular A4.

I had to go into each jpeg and print them from "windows photo", and that should be unnecessary. Maybe I am overlooking a solution, if not, this function should be added.

Regards Hallvard