I am using jSignPDF to sign PDF with a PKCS12 i purchased from COMODO INC. But when viewing the signature in Adobe Acrobat i get, "Signature Verification Failed". How can i sign a PDF and get the Signature Verified?
There is a way for Adobe Acrobat to be instructed to accept (i.e. trust) certificates either individually or trust all certificates issued by Comodo, however, this has to be done on every machine individually - so you will find it difficult to use these signed documents with third parties. It might work if you just need to use the signed documents internally / within a limited distribution.
Individual certificate trust - The user opens the document with Adobe Acrobat or Reader, right-clicks on the signature, chooses Show Signature Properties and then Show Certificate. By clicking on the Trust tab within that dialog box, the user can select Add to Trusted Identities to select whether the credential will be trusted for standard approval signatures and/or certification (publishing) signatures.
Much better option (in my opinion) is to tell Adobe Acrobat to trust all parent certificates in the Windows Certificate Store (Comodo is in this list) - it may also be possible to enable this setting organisation wide by Group Policies etc (but I am not the best person to provide that guidance). For individual machines - Within the Adobe Acrobat Edit menu, select Preferences, and then Security. Click on the Advanced Preferences button, and then on the Windows Integration tab. The user can then choose to either trust certificates in the Store for validating standard signatures and/or certification signatures.
For a signed document to show verified automatically on all Adobe Acrobats (version 9.0 and later) no matter who owns / controls the machine you have to have a certificate issued by one of the companies on the Adobe Approved Trust List - http://helpx.adobe.com/acrobat/kb/approved-trust-list1.html