Why does the validator display an invalid electronic signature?

Often the messages refer to the missing integrity, i.e., the document shows changes after signing the document. For example, elements from the network were downloaded and inserted later. You can avoid it by consistently using the latest PDF/A standard PAdES for the electronic signature. To build up correct PAdES documents, please visit our GitHub: https://github.com/SwisscomTrustServices/AIS/wiki/PAdES-Long-Term-Validation

Kindly note: Eu validators are far from being harmonized. Specific validating portals can still show electronic signatures as invalid, even though they meet the requirements of EU regulation eIDAS. The EU is responsible for such harmonization.