Okular - Okular is a universal document viewer based developed by KDE.
PDFtk - PDFtk is a simple tool for doing everyday things with PDF documents.
Sumatra PDF - Sumatra PDF is a slim PDF/DjVu/EPUB/XPS/CHM/CBR/CBZ/MOBI viewer for Windows.
AutoMetadata - AutoMetadata is a tool for exploring and manipulating metadata, document properties, and viewer preferences in multiple PDF documents.
Foxit Reader - Foxit Reader is a free and light-weight multi-platform PDF document viewer.
Pdfinfo - Pdfinfo is a PDF document information and metadata extractor tool.