AATL certificates for trusted PDF signing and Adobe Reader
Certificates for trusted PDF signature (AATL) are used to sign documents in Adobe Reader. A trusted PDF signature requires a special type of certificate. A signature made with an AATL certificate is fully trusted in Adobe Acrobat.
What is it?
The Adobe Approved Trust List is a program that allows millions of users around the world to create digital signatures that are trusted whenever the signed document is opened in Adobe® Acrobat® or Reader® software. Essentially, both Acrobat and Reader have been programmed to reach out to a web page to periodically download a list of trusted "root" digital certificates. Any digital signature created with a credential that can trace a relationship ("chain") back to the high-assurance, trustworthy certificates on this list is trusted by Acrobat and Reader (source: Adobe.com).
Using AATL certificates for PDF
A document’s electronic signature proves its origin and integrity from the moment it has been signed.
Using AATL certificates are directly required by Adobe for trusted PDF document signing (Adobe has special issuing requirements, see below). If you use a different signature, it will not be trusted in this program and the reader will receive an error. You can sign documents directly in Adobe Reader (no special software us required) by using an AATL electronic signature certificate (which must be stored on HW token).
Getting the AATL certificate
Adobe has special requirements on electronic signature certificates. They must be stored on a secure device, so they are issued exclusively on a token or smart card. To obtain a certificate, you must complete the form, send it to the CA and sign it with the CA representative (eg during a video call). An alternative is a document certified by a notary, which is sent by the certification authority to the certificate’s applicant.
What does a document signature look like in practice?
The screenshot below shows an example of signing an office document.
You can immediately send the newly signed document to the recipient who will know who it was from and that document has not been changed since it was signed.