Converting to PDF/A an existing Signed Document
It is not possible to convert an existing PDF document that is already signed to PDF/A. This is because any changes that you make to a PDF even if it’s only adding PDF/A tags information in the metadata would invalidate the signature. If your PDF is already signed, you will need to remove the signature, convert to PDF/A and then sign it again.

Digitally Signing a PDF/A Compliant Document
It possible to digitally sign a PDF document that is already PDF/A compliant and tagged as PDF/A. The digital signature added will have to follow the PDF/A requirements such as: text on the signature will have to use an embedded font, any image attached to the signature appearance will have to use a permitted color space (deviceRGB or deviceCMYK), etc…

Adding a PDF/A compliant Digital Signature
Unfortunately, at the moment, it is not possible to add PDF/A compliant signatures using Qoppa PDF libraries jPDFProcess or jPDFSecure. However, we have have all the underlying technology to be able to do so. We are working on this feature and this feature will included in the next version. Contact us if you’d like a preview build.