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
PDFTools by SheelApps - PDFTools
GSView - Use Ghostscript GSview to open PDF files with owner password restrictions.
QPDF - QPDF is a command-line program that does structural, content-preserving transformations on PDF...