Alternaly
DOCUMENT VERIFICATION

Verify Your Alternaly-Signed Document

Every PDF we issue is cryptographically signed by signature.alternaly.com. Install our certificate once and your viewer will recognize all Alternaly documents as trusted.

Download .cer (Windows, macOS, Adobe)Download .crt (Linux)
SHA-256 fingerprint
87:34:C0:3D:64:B0:26:E2:5E:E5:F3:2A:2F:6A:C6:53:4C:B5:56:B2:71:AD:D2:28:F9:B7:8D:FD:4C:05:50:15
Issued to: signature.alternaly.com Valid: May 2026 – May 2036
WHY THE WARNING?

Why your PDF viewer shows "signer unknown"

Alternaly runs its own private certificate authority, so we never depend on a third party to sign on your behalf. Your viewer doesn't know our CA yet — that's the only reason it shows a warning.

  • The cryptographic signature on your document is mathematically valid.
  • The warning means "I don't recognize this issuer," not "this document was altered."
  • Trusting our certificate is a one-time step on your device — nothing is sent back to us.
  • If a document had been tampered with, the signature itself would fail — regardless of whether you've trusted the certificate.
Signature Panelloan-agreement.pdf
Signature is valid, but the signer's identity is unknown
Signed bysignature.alternaly.com
Signing time2026-05-25 14:32 EDT
QUICK VERIFICATION

Scan the QR code on the document

Every Alternaly-signed PDF carries a QR code that links to the original on our servers. Scanning it lets you confirm — without installing anything — that the file you have matches the one we issued.

Signed PDFloan-agreement.pdf
  1. 1Open your phone's camera app and point it at the QR code printed on the signed PDF.
  2. 2Tap the link your phone shows.
  3. 3Compare the document that opens with your copy.

Always check the domain

Trusted (must end with alternaly.com)
https://signature.alternaly.com/…Current
https://alternaly.com/…
https://www.alternaly.com/…
https://app.alternaly.com/…
Any future *.alternaly.com with a valid HTTPS certificate
Do not trust
https://alternaly-secure.com/…
https://alternaly.com.verify-now.io/…
https://signature.altemaly.com/…
https://alternaly-docs.net/…
https://signature-alternaly.com/…
PERMANENT TRUST

Trust the certificate on your device

If you receive Alternaly documents often, install our certificate once and your viewer will validate every signature automatically — no scan needed.

1

Download the certificate

Use the .crt or .cer file you downloaded above. Both contain the same public certificate — pick whichever your OS prefers.

2

Install it as a trusted root

Add the certificate to your operating system's trust store. We walk you through every major OS below.

3

Reopen the PDF

Your viewer will now mark Alternaly signatures as trusted. Adobe Reader needs one extra step, covered below.

INSTALL THE CERTIFICATE

Install on your operating system

Pick your operating system below. For Linux we cover Ubuntu/Debian, Fedora/RHEL, and Arch.

Windows

  1. 1Double-click the signature-alternaly.cer file you downloaded.
  2. 2Click "Install Certificate".
  3. 3Choose "Local Machine" (recommended) or "Current User".
  4. 4Select "Place all certificates in the following store".
  5. 5Browse to and select "Trusted Root Certification Authorities".
  6. 6Click Next, then Finish, and confirm the security prompt.

macOS

  1. 1Double-click signature-alternaly.cer — Keychain Access will open.
  2. 2Add it to the "System" keychain (or "login" if you only want it for the current user).
  3. 3Authenticate with your password to confirm.
  4. 4Find the certificate in Keychain Access and double-click it.
  5. 5Expand the "Trust" section.
  6. 6Set "When using this certificate" to "Always Trust", then close the window.

Linux

Open a terminal in the folder containing signature-alternaly.crt, then run the commands for your distribution.

Ubuntu / Debian
sudo cp signature-alternaly.crt /usr/local/share/ca-certificates/
sudo update-ca-certificates
Fedora / RHEL
sudo cp signature-alternaly.crt /etc/pki/ca-trust/source/anchors/
sudo update-ca-trust
Arch Linux
sudo trust anchor --store signature-alternaly.crt
ADOBE ACROBAT READER

Trust the certificate inside Adobe Reader

Adobe Reader keeps its own trust store, separate from your operating system's. Even after installing the certificate on your OS, follow these steps so Adobe also trusts Alternaly signatures.

  1. 1Open any Alternaly-signed PDF in Adobe Reader.
  2. 2Click the signature in the document, or open the Signatures panel on the left.
  3. 3Click "Signature Properties", then "Show Signer's Certificate".
  4. 4Switch to the "Trust" tab and click "Add to Trusted Certificates".
  5. 5Check "Use this certificate as a trusted root".
  6. 6Also check "Certified documents", then click OK to save.

Why the extra step?

Unlike browsers or your operating system, Adobe Reader ships with its own Approved Trust List and ignores the system trust store by default. Trusting the certificate once inside Adobe applies to every Alternaly document you open afterwards.

Acrobat Reader · Trust Settings
Subject: signature.alternaly.com
Issuer: signature.alternaly.com
Valid until: May 2, 2036
FINAL CHECK

Confirm everything looks right

Reopen any Alternaly-signed PDF. If everything is in order, your viewer will display a green check and the message below.

Signed and all signatures are valid.

Tip: always compare the SHA-256 fingerprint shown by your viewer with the one published at the top of this page before trusting the certificate.

At least one signature has problems.

What if the signature is invalid?

If your viewer shows a red "X" or warns that the document has been modified, the file may have been altered after signing. Trusting our certificate will not change this — an invalid signature stays invalid by design. Don't act on the document — contact us and we'll verify it against our records.

Contact us to verify

Still seeing a warning?

Our team can walk you through the install for your specific setup.

Contact Us