Adobe’s program for automatically trusting certificate-based signatures on Portable Document Format (PDF) files in Acrobat and Acrobat Reader. Both products periodically download a list of trusted root digital certificates from an Adobe-hosted page. Any digital signature created with a credential that can chain back to a high-assurance certificate on that list is trusted by Acrobat and Reader.
Certificate authorities (CAs), governments, and businesses apply by submitting application materials and their root certificates. After Adobe verifies that the applicant’s services and credentials meet the published technical requirements, it adds the certificate to the Trust List, digitally signs that list, and posts it. Recipients then see a trusted signature without importing roots themselves. Adobe does not sell signing credentials.
How Trust Is Established
The program is a signed catalog of member roots, not a chain that every credential must share with the Adobe Root. The feature is on by default.
- Application: A CA, government, or business submits materials plus a root or other qualifying certificate.
- Assurance review: Adobe checks services and credentials against the published technical requirements.
- Publication: Adobe adds the certificate, signs the Trust List, and hosts it.
- Client import: Acrobat and Reader download the list on a regular interval and trust signatures that chain to it.
How Acrobat Validates a Signature
When a signed document opens, Acrobat and Reader ask whether the certificate is still valid, whether the file changed since it was signed, and whether the certificate chains to a trusted identity. Revocation is checked with Online Certificate Status Protocol (OCSP) and Certificate Revocation List (CRL) data.
Members and Legal Alignment
Members issue digital signing certificates and timestamp services used with Acrobat, Reader, and Adobe Acrobat Sign. Those credentials are commonly used to meet requirements including the EU’s Electronic Identification, Authentication and Trust Services (eIDAS) regulation. Many members issue credentials suitable for Qualified Electronic Signatures (QES). Certificate-based signatures in PDF files often follow PDF Advanced Electronic Signatures (PAdES).
| Program | Steward | Trust Anchor | Typical Use |
| AATL | Adobe | Adobe-signed list of member roots, downloaded by Acrobat and Reader | Global high-assurance PDF signatures |
| Certified Document Services | Adobe | Chain to the Adobe Root embedded in products | Predecessor program |
| European Union Trust List | EU member states under eIDAS | National lists of qualified trust service providers | Qualified signatures, seals, and timestamps |
