I am sure you are aware that the email software has a search box, and of course so does the browser. Si you might mean the book reader or the magazine stand.
I do not think that they have search facilities, at least I have been unable to find one. I need one for the manual and find it quicker to look things up on my PC.
It would have been sensible for them to provide an index.
While we're slagging them off, I will add something. If you touch a word, and hold it for a second or two, it will be highlighted and some options come up, including a search option telling you page numbers. Also definition and other things. That might be useful.