Yes. I submit a lot of PBs with back matter. Most are NF, but I have even had back matter for a few fiction PBs that I have written. When I submit it, I do a page break, title the back matter, then write it double spaced. You can just call it "Author's Note" but I think editors like to see creativity in the title, too. My PB that sold, I titled the back matter "Who Are These Freaky Fish?" (Though I don't think a creative title will make or break the PB, one editor at a retreat told me she likes to see authors think out of the box and use the book's personality/tone in titling the back matter.)
Good luck!!!!!