Verify signature on open in IE

What default method are you using for verifying your signatures, Adobe Default, or a third party?

I am using Adobe reader that is configured to verify digital signatures when the file is opened.
It works fine with Adobe of course but when I open a PDF that is located in the web, and is signed, I see a question mark untill I explicitly verify the signature

Does the question mark have any other icons (caution triangle, person, or pen)? The question mark is usually associated with not having trusted the certificate, the revocation check could not complete, or a chain could not be built to a trust anchor.

You are right, but this is the question mark of not yet validated, as when I right click and validate it, it becomes a green tick mark

Do you have the following preference checked? Edit --> Preferences --> Security panel "Verify signatures when the document is opened. Do you have the certificate for the signature set to be Trusted?