Here’s a full article (assumes "Elli Bertino" is a researcher/artist working with invisible-PDF techniques): Introduction Invisible PDFs are documents that contain content not immediately visible when viewed normally. This can include hidden text, metadata, overlay layers, invisible annotations, or embedded resources that are not rendered by default. Invisible-PDF techniques are used across accessibility, digital forensics, document security, art, and occasionally malicious activity. ellibertinoinvisiblepdf full
