How do I save a PDF to my iPhone camera roll?

i have communicated with someone and after several communications i was asked to send him some pictures as pdf,

the only way to do that is to open that email and touch its body to pope out the long box and then touch ( insert photo). For me to pick up the pdf from the camera roll.

i know how to save pdf to books but useless if no way for email to pick it up from books .

I don't know if there is a way to save pdf or jpg in to the camera roll .

I would appreciate if anyone knows how to do that to share it with me.