qpdf

qpdf is an open-source command-line tool and C++ library for working with the structure of PDF files. It performs content-preserving transformations and supports splitting and merging documents, encryption, linearization, and structural inspection. It can also create PDFs when the calling application supplies all the content. The project is licensed under the Apache License, Version 2.0 and is maintained by Jay Berkenbilt and Manfred Holger, who hold the copyright with earlier work dating from 2005.

It runs locally, with binary distributions available for Windows, macOS, and Linux, and can be built from source. Building needs a C++ compiler that supports C++20, while linking against the library needs a C++17-compatible compiler. The project says qpdf has very few external dependencies, and is intentionally lightweight. The command line follows the pattern qpdf, input file, options, output file. Password-protected files can be opened with --password, and --split-pages writes separate output files for each page or group of pages.

Its scope is deliberately low-level: it does not render PDFs, extract text, or provide higher-level interfaces for editing page contents. The documentation notes that many programs generate simple PDF files but cannot password-protect or web-optimize them, which is where qpdf is typically applied afterwards. Developers can embed its library in applications.