back page for book

[Jean Baptiste Favre]

Hello,
I'm transcribing an old scores' book into lilypond.
I'd like to get a printable PDF with a cover and a back page.
On the back page, I want to indicate the source of the original score.

If the final PDF has an odd number of pages, I want to add a blank page 
with the footer.
If the book has an even number of pages, I only want the footer to be 
added to last page, without adding a new one.

I'm using book-titling.ly from Nicolas Sceaux for the cover, but I'm 
stuck with the back.
I tried playing with oddFooterMarkup and evenFooterMarkup variable 
without success.

Any idea or advice welcome,
Best,
JB