Encryption Algorithms and Key LengthsPDF encryption makes use of the following encryption algorithms: RC4, a symmetric stream cipher (i.e. the same algorithm can be used to encrypt and decrypt). RC4 no longer offers adequate security and has been deprecated in
PDF DRM how do you know?
How does one know whether a PDF file has DRM? I have some PDF files, I want to check if they are protected by DRM or not, how can I check these PDF files quickly?