Creating Form with Signature Validation Valid

[GullsOnRoof]

I have create a form on Adobe Acrobat DC with digital signature field and sent it out to my colleagues. When it comes back it shows  "Signature not Valid". I don't want to manually validate this every time since its a large numbers of forms.  How can I build the form so it comes back as validated?   I'm not sure if this is a public key and private key issue or how to implement it. I have made several changes to the security settings on the form and it keeps saying 'not validated'.

Your help is appreciated

Lisa

[GullsOnRoof]

additional Info: I have checked the box "Verify Signature When Document Opens" in Both Acrobat and Reader and I still get the "Signature Validity is Unknown".

Lisa

[Bernd Alheit]

Have you the public keys of the colleagues?

[GullsOnRoof]

No I don't have their public keys. Getting their public keys would be the same as having to validate each signature which is what I'd like to avoid because these forms are filled out by thousands of employees on a regular basis due to federal laws.  I've been giving the task of looking for an alternate method to the current application which is Alpha Trust.

I have the creative cloud suite so if there is another application you think I should be using, let me know. 

Thanks

Lisa