Digital Certificate Providers & Certificate Authorities

"Digital certificate provider" is used to mean two different things, and mixing them up leads buyers to the wrong vendor. This guide separates the three categories — certificate authorities (CAs), document signing certificates, and official trusted lists — so you can find the right one for a TLS certificate, a legally recognized signature, or a trusted signer you need to verify.

The three categories, clearly separated

1. Certificate authorities (CAs) issue the cryptographic certificates themselves: TLS/SSL certificates for websites, code-signing certificates for software, and document-signing certificates for people and organizations.
2. Document signing certificates are a specific certificate type issued by a CA and bound to an individual or organization identity. They are what enable advanced (AES) and qualified (QES) electronic signatures, and they appear on trusted lists such as Adobe's Approved Trust List (AATL).
3. Official trusted lists are not vendors — they are the registries that tell you whose certificates are recognized. Examples include the EU eIDAS Trusted List, the Adobe Approved Trust List (AATL), and the Microsoft Trusted Root Program.

A signature platform (DocuSign, Adobe Acrobat Sign, eSign.AI, and similar) is a fourth thing again: it is software that orchestrates the signing workflow and consumes certificates and identity services. If you are choosing between signature platforms, see our digital signature providers comparison instead of this page.

Certificate authorities to know

The list below was reviewed on August 17, 2026 against each CA's public site. It describes what each one issues and where it is recognized; it deliberately omits price points, which vary by certificate type, validity period, and validation level.

• DigiCert — One of the largest commercial CAs. Issues TLS/SSL, code-signing, and document-signing certificates, and operates enterprise PKI. Its document-signing certificates are on the Adobe AATL.
• GlobalSign — A long-established CA offering TLS/SSL, code signing, and document signing. It also operates qualified trust services in the EU, placing its qualified certificates on the eIDAS Trusted List.
• Sectigo — The CA formerly known as Comodo CA. A high-volume issuer of TLS/SSL, code-signing, and document-signing certificates, including AATL-listed signing certificates.
• Entrust — Focuses on enterprise PKI, TLS, code signing, and hardware-backed identity, serving regulated and government environments.
• IdenTrust — A bank-focused CA whose document-signing certificates are recognized on the Adobe AATL; commonly used in finance and government.
• SSL.com — Issues TLS/SSL, code signing, and AATL-listed document-signing certificates, with an emphasis on automation and developer access.

This is not an exhaustive list; other CAs exist, and the right choice depends on the certificate type and the region where the signature must be recognized.

Document signing certificates: what to check

If your goal is a signature that Adobe Acrobat or Reader marks as valid and trusted, the signing certificate must chain to a CA on the Adobe Approved Trust List (AATL). If your goal is a qualified electronic signature (QES) in the European Union, the certificate must come from a qualified trust service provider (QTSP) listed on a national eIDAS Trusted List.

Key checks when buying a document signing certificate:

• Which trusted lists include the issuer (AATL, eIDAS QTSP, Microsoft Trusted Root)?
• Is the certificate bound to an individual or an organization, and how is identity verified?
• Does the certificate require a hardware token or cloud signing, and does that fit your workflow?
• What validity period and renewal process apply?

Official trusted lists: how to verify a signer

• EU eIDAS Trusted List — Each EU member state publishes its list of qualified trust service providers. Use it to verify whether a certificate is qualified (QES) rather than simple (SES) or advanced (AES).
• Adobe Approved Trust List (AATL) — Lists CAs whose document-signing certificates Adobe Acrobat and Reader treat as trusted; it is the practical test for PDF signatures.
• Microsoft Trusted Root Program — Governs which root CAs Windows trusts, relevant to code signing and some document-signing scenarios.

When a signed document arrives, checking the certificate against the relevant trusted list — not the signer's word — is what establishes whether the signature will hold up.

How this differs from choosing a signature platform

A CA issues certificates; a signature platform runs the workflow. In practice most organizations buy both: a platform for day-to-day signing, and a CA or QTSP service for the higher-assurance signatures that need a recognized certificate. If you are choosing a platform, start with our digital signature providers comparison. If you need HIPAA-specific guidance, see our HIPAA-compliant eSignature guide.

Checklist

1. Decide which certificate type you need: TLS/SSL, code signing, or document signing.
2. For PDF signatures, confirm the issuer is on the Adobe AATL.
3. For EU QES, confirm the provider is a QTSP on the eIDAS Trusted List.
4. Confirm identity verification, hardware vs. cloud signing, validity, and renewal terms.
5. Verify inbound signatures against the trusted list, not just the signature's appearance.