Best Open-Source PDF Mergers 2026: 6 Options Compared

Combining PDFs is a solved problem, and open-source tools offer it in every shape. If you want a window with drag and drop, PDFsam Basic and PDF Arranger do the job: PDFsam splits, merges, mixes and rotates in separate modules, while PDF Arranger lets you see thumbnails and move pages around. Stirling PDF merges inside a browser interface and can run on your own server if you need to keep documents private. For scripts and automation, qpdf, pdfcpu and pypdf are the standard choices: qpdf and pdfcpu are command-line programs (pdfcpu is a single Go binary), and pypdf is a Python library for building merging into your own code. A merge is lossless in the sense that pages are copied, but bookmarks, form fields and attachments may not all carry over, so inspect a result before deleting the originals. Password-protected files must be unlocked first. For a once-a-month merge, any GUI will do; for a thousand files nightly, pick a command-line tool and a small script. Online mergers upload your files to a server, so offline tools are the better choice for contracts and personal documents. Licences below come from the projects' own repositories as of the check date.

PDFsam Basic

AGPL-licensed desktop app with separate modules to merge, split, mix and rotate PDFs. A free basic edition is the focus here.

Price: Free (PDFsam Basic is free and open source; an Enhanced edition with a full editor is a yearly subscription) (PDFsam Basic pricing, checked 2026-10-23).

Platforms and license: Windows, macOS, Linux. AGPL (open source) (license source).

Best for: Simple desktop merging.

PDF Arranger

GPL-3.0 visual tool to merge or split PDFs and rearrange, rotate and crop pages from thumbnails.

Price: Free (Free and open source desktop app) (PDF Arranger pricing, checked 2026-10-24).

Platforms and license: Desktop (Python/GTK). GPL-3.0 (open source) (license source).

Project activity: 6k GitHub stars · latest release 1.14.0 (May 23, 2026) · last commit Oct 1, 2026

Best for: Merging with page-by-page control.

qpdf

Apache-2.0 command-line tool and library for transforming PDFs; merging and splitting are listed among its features.

Price: Free (Free and open source command-line tool and library) (qpdf pricing, checked 2026-10-24).

Platforms and license: Command line. Apache-2.0 (open source) (license source).

Project activity: 5.5k GitHub stars · latest release v12.4.2 (Sep 27, 2026) · last commit Sep 26, 2026

Best for: Scripts and servers.

Worth knowing: README says it can split and merge files, among other transformations. License taken from the repository metadata and LICENSE file; description from the project README. No paid plan was checked.

pdfcpu

Apache-2.0 Go tool whose README shows a one-line merge command; also validates, optimizes and splits files.

Price: Free (Free and open source command-line tool and Go library) (pdfcpu pricing, checked 2026-10-24).

Platforms and license: Command line, Go library. Apache-2.0 (open source) (license source).

Project activity: 8.9k GitHub stars · latest release v0.16.4 (Oct 27, 2026) · last commit Oct 27, 2026

Best for: A single-binary command-line merge.

Worth knowing: README lists validate, optimize, split, trim and merge. License taken from the repository metadata and LICENSE file; description from the project README. No paid plan was checked.

pypdf

BSD-style Python library for splitting, merging and cropping PDFs. You write code; there is no interface.

Price: Free (Free and open source Python library) (pypdf pricing, checked 2026-10-24).

Platforms and license: Python library. BSD-3-Clause style (see LICENSE) (open source) (license source).

Project activity: 10.3k GitHub stars · latest release 6.21.3 (Oct 27, 2026) · last commit Oct 27, 2026

Best for: Merging inside Python programs.

Worth knowing: GitHub reports the LICENSE as non-standard (Mathieu Fenniak copyright, BSD-style text); read it before redistributing. Project describes itself as a library for splitting, merging and cropping PDFs.

Stirling PDF

MIT with some directories under separate licences. Merge sits among 60+ tools in a web interface and the free plan lists 1,000 monthly credits.

Price: Free (Free plan at $0 with no card: web, desktop and self-hosted use, 60+ PDF tools and 1,000 monthly credits); paid from $99 per month (Team, 100 users) (Stirling PDF pricing, checked 2026-10-23).

Platforms and license: Web browser, Desktop app, Self-hosted (Docker). MIT, with some directories under separate licenses (open source) (license source).

Project activity: 95.2k GitHub stars · latest release v3.2.2 (Oct 24, 2026) · last commit Oct 27, 2026

Best for: Merging plus other tasks in one place.

Worth knowing: LICENSE file says MIT except app/proprietary and other directories with their own licenses. Repository README lists edit, merge, split, sign, redact, convert, OCR and compress.

Which one to pick

• You merge a few files by hand once in a while: PDF Arranger
• You need to reorder pages from many sources visually: PDFsam Basic
• You merge hundreds of files from a script: pdfcpu
• You build merging into a Python app: pypdf