Read the FAQ: https://www.pdf-insecurity.org/other/faq.html https://www.pdf-insecurity.org/other/faq.html Basically they tested almost everything you could thi

Read the FAQ: https://www.pdf-insecurity.org/other/faq.html https://www.pdf-insecurity.org/other/faq.html Basically they tested almost everything you could think of, but none of the major open source viewers supports PDF signature verification in the first place.