Document Signing Certificates

‘At Least One Signature Is Invalid’: How to Fix an Invalid Signature in a PDF (Adobe)

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Learn what causes this PDF-related error in Adobe Acrobat and Reader and how to fix it

Since you’re here reading this article, I’ll assume that you’ve received an error informing you that “at least one signature is invalid” in a PDF in Adobe Acrobat (which looks like this):

Invalid signature in a PDF example: A screenshot of how the PDF signature invalid error displays in an Adobe Acrobat PDF
Image caption: A screenshot of the PDF signature error in Adobe Acrobat, which states that “at least one signature is invalid.”
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