PDFTK Builder - PDFTK Builder is a free graphical interface to for PDFTK, making it much easier to use.
Okular - Okular is a universal document viewer based developed by KDE.
PDFTools by SheelApps - PDFTools
Sumatra PDF - Sumatra PDF is a slim PDF/DjVu/EPUB/XPS/CHM/CBR/CBZ/MOBI viewer for Windows.
QPDF - QPDF is a command-line program that does structural, content-preserving transformations on PDF...
Foxit Reader - Foxit Reader is a free and light-weight multi-platform PDF document viewer.