PDFtk - The PDF Toolkit
PDFtk is a simple tool for doing everyday things with PDF documents. It comes in three flavors: PDFtk Free, PDFtk Pro, and our original command-line tool PDFtk Server.
PDF Tools
PDF Split And Merge
A free and open source software to merge, split, rotate and extract pages from PDF files
XpdfReader
Xpdf is a free PDF viewer and toolkit, including a text extractor, image converter, HTML converter, and more. Most of the tools are available as open source.
Free PDF Reader - Sumatra PDF
Sumatra PDF reader and viewer for Windows
BentoPDF - Free Online PDF Tools
Free online PDF toolkit with 100+ tools. Merge, split, compress, convert PDFs - 100% browser-based, no signup, unlimited files, privacy-first.