PDFTK Builder - PDFTK Builder is a free graphical interface to for PDFTK, making it much easier to use.
QPDF - QPDF is a command-line program that does structural, content-preserving transformations on PDF...
GSView - Use Ghostscript GSview to open PDF files with owner password restrictions.
iSafePDF - iSafePDF is a free open source PDF protection software.
A-PDF Restrictions Remover - For 9.99 $ A-PDF Restrictions Remover is extremely easy to use.
PyPDF2 - PyPDF2 - A utility to read and write pdfs with Python