Problem signing with digital certificate in adobe acrobat reader on Macos

[Andrés34613331dm09]

Although I have the certificate correctly imported in the mac keychain, I always get the same error message:

The credential selected for signing is invalid.

The certificate is correctly loaded. This video describes the same problem:

https://www.youtube.com/watch?v=aW6UevLRsU8&t=33s

They give a temporary solution which is to load the certificate through acrobat but you should import it correctly with the macOS keychain.

[S. S]

Hi @Andrés34613331dm09,

Hope you are doing well. Sorry for your experience with using digital certificates on Acrobat.

Let's understand why this happens: 

On macOS, Acrobat Reader relies on a plugin interface to access certificates stored in the Keychain Access. But there are limitations or mismatches in how Reader interfaces with:

• PKCS#12 (.p12/.pfx) files,

• S/MIME or Qualified Certificates, and

• Keychain Access permissions for private key usage.

In some cases, Reader does not gain permission to access the private key, even though it appears in the certificate list.

Now, let's look at a fix we can try:

1. Export the certificate from Keychain as a .p12 (PKCS#12) file:

   • Open Keychain Access.

   • Right-click your certificate > Export as .p12.

   • Include the private key and set a password when prompted.

2. In Reader:

   • Go to Preferences > Signatures.

   • Under Identities & Trusted Certificates, click More.

   • Click Digital IDs > Add ID.

   • Choose A File, then select your .p12 file and enter the password.

After this, the certificate should work correctly for signing.

Also, if the certificate uses a QES, you will need to download a valid PKCS#11 module or cloud signature provider from the issuing authority. More info here: https://adobe.ly/3FTHmYK.

Hope this clarifies your concern.

Regards,
Souvik.