PDFsam Basic

Online "merge PDF" websites are a serious exposure. Contracts, scanned ID documents, medical reports, company files — an enormous amount of sensitive material gets casually uploaded to free sites, with no way to know how long it is kept, who sees it, or whether it becomes training data.

PDFsam Basic does the same job while the files never leave your computer. AGPL-3.0, 4,539 stars.

Its scope is deliberately narrow — page-level PDF operations:

• Merge: combine several PDFs, choosing which pages come from each file, preserving or rebuilding the bookmark outline.
• Split: by a fixed page count, by bookmark level, or at specified pages. Cutting a scanned document into chapters is a common need.
• Extract pages: take only pages 3, 7 and 12–20 into a new file.
• Rotate: batch-correct sideways scanned pages.
• Alternate mix: a genuine lifesaver — scanning a double-sided document on a single-sided scanner leaves you with a front-pages file and a reverse-order back-pages file, and this interleaves them back into the correct order.

The interface is plain but clear, with drag-and-drop batching and fast processing.

Two things to state:

• It only manipulates pages; it does not edit content. Changing text inside a PDF, annotating or filling forms is out of scope — that is Xournal++ (handwritten annotation), Okular (annotations) or LibreOffice Draw (light editing). For a fuller PDF toolbox with OCR, compression and conversion, see Stirling-PDF.
• It has a paid sibling. PDFsam Enhanced and Visual are commercial products from the same developer with more features, and the app mentions them. That is a developer describing their own product rather than third-party advertising, and it does not restrict Basic in any way — Basic is complete, with no page limits, watermarks or trial period.

It is a Java application, but the official installers bundle a runtime, so no separate JDK is needed.