qpdf

Low-level, content-preserving PDF structure tool: linearizes PDFs for fast web view, encrypts and decrypts, splits and merges files, inspects and edits PDF object structure directly, and repairs damaged files without altering actual page content. Explicitly does not render pages or extract text — its own documentation is clear this is a structural transformation tool, not a content-reading one, and points elsewhere (e.g. the `pdftools` R package) for extraction needs.