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PDF Joiner - This online tool allows you to join several PDF documents into a single file, free of charge.
PDFsam - PDFsam Basic, a free, open source, multi-platform software designed to split, merge, extract pages, mix and rotate PDF files
PDFChef Merge PDF - PDFChef Merge PDF is an online tool that allows you to merge multiple PDf files into one quickly and securely.
Clipperly - Convert, edit or optimize your files online. More than 400 different formats supported among documents, images, spreadsheets, ebooks, archives, presentations, audios and videos.
PDFill - Open, View, Edit, Save and Print PDF Documents without Adobe Acrobat