We go to great lengths to maintain PDF/A compliance throughout the signature process, taking special care of signature appearance that have transparency and making sure the text that is displayed next to the signature (ex.: date) uses a font that is embedded in the PDF/A document.
Unfortunately, Adobe doesn’t go to the same length. Signature appearances are embedded “as-is” even if they have transparency, and they do not embed the font used to display the text next to the signature appearance. The result is that a PDF/A compliant file becomes non-compliant. Both ConsignO Desktop and Adobe Acrobat DC can be used to test PDF/A compliance of the document.
When defining a signature appearance, use a JPG file (which doesn’t have transparency) and remove/uncheck all text to be displayed next to your signature.