iSafePDF - iSafePDF is a free open source PDF protection software.
PDFTK Builder - PDFTK Builder is a free graphical interface to for PDFTK, making it much easier to use.
PDF Unshare - pdf unshare, pdf protection, protect, share, updf, prevent, Lock PDF, Encrypt PDF, PDF Access, Lock, PDF, Encrypt, Access
QPDF - QPDF is a command-line program that does structural, content-preserving transformations on PDF...
PyPDF2 - PyPDF2 - A utility to read and write pdfs with Python
PDFEncrypt - PDFEncrypt is a free, open-source Windows application that encrypts any PDF file using...