I’ve just spent 10 minutes looking for the print function when trying to print an email in iOS13/iPadOS13. I kept looking for the Share Sheet, and it’s nowhere to be seen. I found the print command in the end, and to access it you will find it under the ‘reply’ button. It’s actually right at the bottom of the list and you don’t see it unless you scroll to the bottom. Excuse my ignorance if you already new this, but it really had me going for a while!