Tracking PDF files

More fun publisher surveillance:
Elsevier embeds a hash in the PDF metadata that is *unique for each time a PDF is downloaded*, this is a diff between metadata from two of the same paper. Combined with access timestamps, they can uniquely identify the source of any shared PDFs. pic.twitter.com/D9KxnXkMVu

— 𝚓𝚘𝚗𝚗𝚢﹏𝚜𝚊𝚞𝚗𝚍𝚎𝚛𝚜 (@json_dirs) January 25, 2022