How do I Resolve the "At least one signature has problems" error in Adobe Reader?

Suppose the error "At least one signature has problems" appears in Adobe Reader. In that case, it means that the security certificate used to sign the document in which Adobe reports the error is not a trusted identity in your Adobe reader.

There can be several reasons why the certificate is not approved. We will review the various reasons below. Depending on the device you are using and the Adobe Reader version, there may be different ways to solve this problem.

What does the error message mean? 
Update document to Adobe Standards
Make the certificate a trusted identity in your Adobe reader
If making the certificate a trusted identity doesn't work

What does the error message mean?

The error message "At least one signature has problems." appears in a bar at the top of Adobe Reader. This means that Adobe cannot recognize the certificate used to sign the current document.

The error message at the top of Adobe Reader says that something is wrong with the signature
The signature panel can be accessed by clicking the button on the right, where more details about the actual signing, the certificate used and identity information about the signer appear.
In this case, the panel shows that the signature is valid but that the signer's identity is unknown, which is contrary to AATL and the EUTL certificates used for digital signers and the eIDAS regulation.

If you experience this error, it can therefore mean the following:

The certificate used to sign is not an AATL/EUTL certificate
The signer's identity is not captured and embedded in the document
The certificate is not an LTV (Long Term Validation) document - This requires a time stamp for the signature.

A very common reason for this problem is that the original PDF (Before the Signature) contains design elements that are not supported by Adobe. These can be design elements or javascript that cause images or fonts to change when the document is opened in Adobe.

We will now guide you through how to "fix" the document, in order to avoid this issue with future signings.

Update the document to Adobe Standards

If the PDF was made in an older version of Adobe Acrobat, or some other form of file editing program, Adobe may have an issue validating the signature, as the document is altered once Adobe opens it, with the signature.

Certain Fonts, colors or images may cause this issue.

Note - this report code and description, does not always show, even if this issue is the case.
The following fix does not alter the document in any way that simply signing the document usually wouldn't, but it does ensure that when the document is signed, it will verify the signature correctly.

Open the original Non-signed document, and click File in upper right hand corner
Click Print
Select the printer: Microsoft print to PDF
Click Print.
The document is now saved as a PDF file (again) this time however, any elements that would not have been shown properly by Adobe, (And changed after signing!) are changed to adobe standards.

The error should now be fixed.

We will now go through other possible issues, that aren't related to the design of the file.

Make the certificate a trusted identity in your Adobe reader

If Adobe Reader reports the error "At least one signature has problems." and that this only has something to do with Adobe not knowing the certificate, but that it is an approved certificate, you can follow this guide to get the certificate approved in your Adobe Reader.

Note: Although this error appears in Adobe Reader, all signatures can be valid and legally binding.

The guide below is a step-by-step guide on how to fix the problem.

Tap the "Signature Panel" button at the top of your PDF where the error is.
Then press "Validate All" in the signature panel on the left
In the pop-up that appears, press "OK" to validate all signatures in the document.

Once all signatures are validated, it will display a success message depending on the settings.

If the signatures are successfully validated, Adobe Reader displays that the documents are signed and all signatures are valid. If so, you can skip the next steps. however, I would recommend that you take a look here, to see what you can so in the future

If the error "At least one signature has problems" is still visible, it requires us to go into the settings for a signature, by browsing the certificate.

Tap on "Signature Panel" if it is not already open
Right-click with your mouse on the signature that reports an error
select “Show signature properties…”

When you have pressed "Show signature Properties..." a pop-up will appear, in the pop-up you must access the signing certificate

Press "Show Signer's Certificate..." after which you can see information about the certificate.

In the next window, you have the option to add the certificate to Adobe Reader's list of trusted certificates - that is, if this is a valid certificate.

Select the "Trust" tab in the "Certificate Viewer" window, where you can now see that the certificate is not trusted.
Click "Add to Trusted Certificates..." and when Adobe asks if you are sure, click "ok"

Another pop-up will appear where it is possible to mark that this certificate is trusted.

Tick "Use this certificate as a trusted root" then press "OK"
Next, press "OK" again to close down the certificate settings and you can press "Validate all" in the Signature panel.

If making the certificate a trusted identity doesn't work

If you have followed the guide above and it is still not possible to validate the signature, this is because you are using a signature solution that does not meet all requirements for offering a digital signature.

Addo Sign supports all applicable requirements within PaDES, eIDAS and local rules for signatures with eID and simpler signature forms.

You can create a free account here