The CEU Cardenal Herrera University issues a wide range of documents which are digitally signed. To verify the authenticity of these documents, you should first check the details included on them. Then, you can check the verification code they contain via the following link:
Digitally signed documents are fully valid in Spain and, since 1st July 2016, in the majority of countries in the European Union, in accordance with Regulation (EU) No 910/2014 of the European Parliament and of the Council of 23 July 2014 on electronic identification (updated in 2017).