Insert a section break *before* the endnotes. Set the endnotes
to appear at the end of the section (instead of at the end of the
document). Place your appendix after the section break.

LAC wrote:

I am working on a document where I have used automatic endnotes. This
document also requires an appendix AFTER the reference section where the
endnote references are placed. I cannot insert any page breaks after the
reference section. Is there any way to place something after the endnotes?
I can't even insert a section break.