Fix the Credential Selected Is Invalid Error for PDF Signatures in Acrobat on Mac
Question details
The user encounters a "Credential Selected Is Invalid" error when attempting to apply a digital signature to a PDF using a CAC, smart card, or macOS Keychain certificate.
- Product
- Adobe Acrobat
- Device & OS
- macOS
- Scenario
- Digitally signing a PDF document using a smart card (CAC) or Keychain certificate.
- Observed behavior
- The application displays a "Credential Selected Is Invalid" error message and fails to apply the digital signature to the document.
Ensure your macOS is fully updated and that your smart card reader is securely connected to your Mac before proceeding with troubleshooting.
Update Smart Card or CAC Drivers
Outdated drivers are a primary cause of smart card credential errors. Updating the driver ensures compatibility with newer Acrobat and macOS versions.
Acrobat relies on the system's underlying driver to communicate with hardware authentication devices. If the driver is outdated, the credential request will fail.
Safely unplug your smart card reader or CAC from your Mac.
Navigate to the official manufacturer's website for your CAC or smart card reader and download the latest driver compatible with your specific macOS version.
Run the driver installer, follow the on-screen prompts, and restart your Mac to apply the changes.
Reconnect the reader, open your PDF in Acrobat, and attempt to digitally sign the document again.
Use a System File Certificate Instead of Keychain
If macOS Keychain permissions are blocking access, creating and using a local system file certificate can bypass the error entirely.
Check Keychain Permissions and Acrobat Version
Incorrect access controls in Keychain or outdated Acrobat software can restrict communication between the credential and the application.
Digitally Sign PDFs Seamlessly with WPS Office
Bypass complicated macOS Keychain and Acrobat credential errors by using WPS Office's built-in PDF tools to securely and easily apply digital signatures to your documents.
- 1. Open your PDF: Download and launch WPS Office, then open the PDF document you need to sign.
- 2. Access the Protect tab: Navigate to the 'Protect' tab on the top ribbon menu and select 'Sign Document' or 'Digital Signature'.
- 3. Select your certificate: Choose your preferred digital ID file from your local storage or create a new one instantly.
- 4. Apply the signature: Draw the signature box on the desired location of the page and enter your password to finalize the digital signature.
Frequently Asked Questions
Why does my digital certificate work as a file but not from the Mac Keychain?
Mac Keychain relies on specific permissions and driver integrations to communicate with third-party apps like Acrobat. If permissions are restricted or drivers are outdated, Acrobat cannot read the Keychain credential, whereas directly selecting a file bypasses the macOS Keychain bridge entirely.
How do I check my Adobe Acrobat version on a Mac?
Open the application, click on 'Acrobat' or 'Acrobat Reader' in the top menu bar next to the Apple logo, and select 'About Adobe Acrobat'. A window will appear displaying your exact version number (e.g., Continuous Track 2020.009).
What is a CAC and why do I need a driver for it?
A Common Access Card (CAC) is a specialized smart card used for secure authentication, frequently used by government and military personnel. To enable your Mac and PDF software to read the certificate encrypted on the card, you must install the specific driver provided by the card or reader manufacturer.
