I use Asciidoctor PDF 1.5.0.alpha.16 using Asciidoctor 2.0.7 and I read
https://asciidoctor.org/docs/user-manual/#auto-generated-idswith this asciidoc text:
[appendix]
== Maintenance - Vérification ==
I think the good reference is
<<_maintenance_v_rification,Maintenance - Vérification>>
It works from AsciidoctorFX but not with asciidoctor-pdf, I get
asciidoctor: INFO: possible invalid reference: _maintenance_v_rification
and the text is generated as link in pdf document but the link is dead. I tried the other syntax
<<_maintenance_vrification,Maintenance - Vérification>>
wit no success.