I'm trying to download all PDF files from
<https://www.adac.de/_ext/itr/tests/Autotest/> but always get: 

"Forbidden" (403) at link <https://www.adac.de/_ext/itr/tests/Autotest/> (from
primary/primary)

It is possible to download a PDF when I enter the direct link like:
<https://www.adac.de/_ext/itr/tests/Autotest/AT0769_Alfa_Romeo_147_16_Twin_Spark_ECO_Progression/Alfa_Romeo_147_16_Twin_Spark_ECO_Progression.pdf>

Links can be found at
<https://www.adac.de/infotestrat/tests/auto-test/select.aspx> after selecting
"Hersteller" and "Modell".

I already tried different Browser IDs but keep getting the 403 error.

Any suggestions?
Thanks,

Simon