There is a recurring problem with PDF files produced by either pdftex or luatex in France.

Whenever PhD thesis documents are submitted to the French national archives, they have

to be validated by some automated process which relies on pdftk (apparently).

And files compiled by pdftex/luatex are rejected.

The problem is described here :

French pdftex/luatex users will have an eternal gratitude to whoever will 

make this work :-)