When you receive a signed document, you may want to validate its signature(s) to verify the signer and the signed content. Depending on how you have configured your application, validation may occur automatically. Signature validity is determined by checking the
authenticity of the signature's digital ID certificate status and document integrity:
Authenticity verification confirms that the signer's certificate or its parent certificates exist in the validator's list of trusted identities. It also confirms whether the signing certificate is valid based on the user's Acrobat or Reader configuration.
Document integrity verification confirms whether the signed content changed after it was signed. If content changes, document integrity verification confirms whether the content changed in a manner permitted by the signer.
Steps to Validate Digital Certificate:
Download Acrobat Reader DC
Then Open Unverified PDFwith Acrobat Reader DC and Click on question mark and a "Validity Unknown" or "Signature not verified!" message
Now Click on Signature Properties...
In Signature Properties Click on Show Signer's Certificate
Now in Trust Tab Click on Add to Trusted Certificates...
Click Ok on Acrobat Security popup...
In Import Contact Setting popup Check all Check boxes and click OK
Then also click OK on Certificate Viewer Window and Finally Click on Validate Signature ..
& Digital Signature is Valid now...
Last Step to make it permanent. Click on Print icon or press CTRL+P to open Print Windows and select Any PDF printer like I used Microsoft Print to PDF and print document. If you Do not have any PDF printer then download this one :
It will ask to Save file. This is your PDF with Validated Digital Certificate