In today’s world digitally signed documents are quite popular and easy to circulate. We often received this type of PDF documents from online or other sources. After open the document we may notice that the signature which has been signed digitally is showing validity unknown. We can solve this issue very easily by following the procedure as below.
Right click on the actual signature and choose ‘Show Signature Properties‘
On the Signer Info tab, click on ‘Show Signer’s Certificate’
Verify that there is a certification path named end with CA‘.
Mark the certification path and click the ‘Trust’-tab and then ‘Add to Trusted Identities‘. Click ‘OK’ to any security question that comes on next screen
Check the field for ‘Use this certificate as a trusted root‘ and click ‘OK’ twice to close this and the next window. Click ‘Validate Signature‘ to execute the validation.
Once a signature is validated against a trusted certificate, it will show a green tick mark on it.