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Verifiying the Electronic Signature

In order to check signatures for their authenticity or their trustworthiness, you should download and update the European Union Trust List (EUTL).

  1. To do this, navigate to Edit > Preferences within Adobe Reader or Acrobat and then select the “Trust Manager” category.
  2. In the “Automatic European Union Trusted Lists (EUTL) updates” section, make sure that “Load trusted certificates from an Adobe EUTL server” is checked.
  3. Confirm the change by pressing "OK".

If Adobe continues to show the signature as “unknown”, you can initiate an update of the trust services using the “Update Now” button.

Integrate root certificate - old procedure

In order to check signatures for their authenticity or their trustworthiness, you have to integrate the DFN root certificate or the Telekom root certificate of the University of Cologne into Adobe.

Please follow these steps:

1. Download this .fdf file: Root certificate

2. Open the file using Adobe Reader or Adobe Acrobat.

3. A window opens, click on Kontakte zur Liste der vertrauenswürdigen Identitäten hinzufügen.

View of the dialog window described above. The Add Contacts to List of Trusted Identities List button is highlighted at the bottom left.

4. Choose a certificate in the upper field under "Kontakte". In the field below click on the corresponding entry and then Vertrauenswürdigkeit

View of the following dialog window. Three areas are highlighted and numbered 1-3. No. 1 shows the possible contacts, No. 2 the associated certificates and No. 3 the Trust button.

5. Check the following boxes and confirm with OK.

  • "Dieses Zertifikat als vertrauenswürdigen Stamm verwenden"
  • "Zertifizierte Dokumente"
View of the next dialog window as described above. The necessary clicks are numbered 1-3: 1. Use this Certificate as a Trusted Root, 2. Certified Documents, 3. the OK button.

6. Repeat these two steps for all three certificates and click Importieren to finalise.

New view of the previously described dialog window showing the list of contacts and associated certificates to be imported. Below the list of certificates, toward the right side, the Import button is highlighted.

7. Confirm the following prompt with OK.

View of the described pop up Import complete. The OK button is highlighted.

8. Now open the PDF document to be checked in Adobe Reader or Adobe Acrobat. The default settings now automatically verify all electronic signatures in the document. This may take a while. A blue indicator bar will then appear below the menu bar. If you see a green tick and the text „Unterschrieben und alle Unterschriften sind gültig“ in this blue indicator bar, you can assume that the signature(s) applied are valid and trustworthy.

View of the blue indicator bar described above, confirming that the document is signed and all signatures are valid and trustworthy.

9. If you receive an error message instead, please check the possible reasons using this overview compiled by the data center: Error messages