pdfCipher is a speedy and light solution for adding, modifying, and removing standard security settings of PDF documents by batch (Encrypt PDF). Both 40bit and 128bit mode are supported. Proper owner password is needed for modifying or removing existing security settings. It is standalone command line tool. No need of other extra applications or modules.

It supports Windows 9x, NT4, 2000/XP and later. The unregistered version will put a small trial watermark on the first 20pages of the encrypted PDF. Use -R option to enter registration key. After that, no trial watermark will be stamped on the PDF processed.