Validate a digital signature
By configuring digital signatures validation preferences, you can enable validating signatures automatically when the document is opened. See Status icons for PDF documents for details. You may also manually validate the signature if it is unverified or of unknown origin. If the signature status shows validity unknown, you need to contact the signer about the problem.
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Open a PDF document that contains a signature.
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The signature validation occurs automatically if you have already enabled verifying the signature at startup. Otherwise, do the following to manually verify signatures:
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Click on the signature field to validate the signature.
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Right-click on the signature field and select Verify Signature.
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Right-click on the signature you intend to validate in the Signatures panel and select Verify Signature from the menu.
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The Validation Status dialog box appears, describing the validity of the signature. For more information about the signature, right-click on it and select Properties....
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Check the signed versions of the document if the document has been modified after the signature was applied. Also, you may compare the signed version to the current version of the document to see the differences between the two versions. See View previous versions of a digitally-signed document for details.
