You are also supposed to be able to open the attachment section and see the signature details:
In some versions of Adobe Reader there can be an error message claiming that the certificate is invalid, although it´s not. This is a known problem that you can read more about here. This means that Adobe only validates against it´s own trust list AATL, while our certificate is EU issued and must be validated against EUTL.
This does not neccessarily mean that there is something wrong with your signed document, but if you want to be sure you can also use our own validation tool.
Our validation tool is built with code from the EU project Esig/DSS.
In the background, the validation tool first makes a technical check of the signatures formal authenticity, that the document has not been changed and so on. Then it goes online and checks the validity of each certificate in the certificate chain.
This lookup is made live towards the EU Trust List.