If you want to use InterformNG2 to digitally sign invoices as required in Portugal, then you should use the workflow component, DigitalSign cloud PDF signing.
Before you use this component you however need to setup a DigitalSign Server in the tenant settings under Workflow settings as described below.
The reference name for the server configuration. You should use this in the DigitalSign HSM Cloud settings parameter on the workflow component, DigitalSign cloud PDF signing.
The base API URL of the DigitalSign HSM Cloud server. (for instance https://qscd.digitalsign.pt)