Artifex Software
SmartOffice - View & Edit MS Office files & PDFs
FreeSmartOffice is an intuitive, easy-to-use document editing application with a sleek design inspired by the familiar UI of a desktop Office document.
AndroidMuPDF for Linux
FreeAllow you to view PDF documents with parser or rendering library.
LinuxMuPDF
FreeView PDF documents with parser or rendering library.
WindowsAFPL Ghostscript
Freeengine for the interpreter for PostScript and PDF
Mac