Interested in Language
I found this definition of "appendix" here.
"a section giving extra details at the end of a book, part of a book, or document"
If it's another document or leaflet, not a "section" in the same document, can't it be called an "appendix", and should it be an "attachment"?
How about an "annex"?
Usually, if it is a book, we would use "appendix". If it is an e-mail document, we would usually use "attachment. There is a dictionary definition for "annex" that covers these uses, but we usually use "annex" for an addition to a building.
Pope of the Dictionary.com Forum