For best results, use the Preview Document feature when you sign documents. This feature analyzes the document for content that may alter the document’s appearance, and then suppresses that content, allowing you to view and sign the document in a static and secure state.
When you view a PDF in Preview Document mode, a document message bar lets you know if the PDF complies with the PDF/SigQ Level A and Level B specification. Level A indicates that the document contains no dynamic content that can alter its appearance. Level B indicates that the document contains dynamic content that can be suppressed during signing. If the document doesn’t comply with Level A or B, you may want to refrain from signing the document and contact the document author about the problem.
You can also use Preview Document mode outside of a signing workflow to check the integrity of a document.