PDFCreator is a free tool to create PDFs easily from nearly any application. With the PDFCreator Printer driver you turn any program into a PDF-machine
PDFCreator is released under the term of th GPL (GNU General Public License).
PDFCreator offers multilingual support, so anyone who wants to contribute a language can edit one text file and enjoy his own language. Every language that is sent to me will be included in the next release.
http://sourceforge.net/projects/pdfcreator/
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PDF Blender is a free cross platform PDF merging tool. A perfect companion to PDFCreator.
http://www.spaceblue.com/pdfblender/