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SumatraPDF

Free, open-source, lightweight PDF and ebook reader for Windows.

Jobs View Convert Compress Merge Edit Protect Sign

Since 2006

Operated by Krzysztof Kowalczyk

Visit SumatraPDF

Opens the vendor's own site.

Jobs covered

Open a task to see exactly what the vendor documentation supports.

View Browse all view tools

viewing documents with SumatraPDF, where the current stable 3.6.1 release documents support for PDF, EPUB, MOBI, comic-book archives CBZ and CBR, DjVu, XPS, CHM and images, with tabs and windows, viewing modes, scrolling and zooming, thumbnails, text search, hyperlinks, favourites, printing and read-aloud, in a native Windows 7, 8, 10 and 11 application with 32-bit, 64-bit and ARM64 builds and a portable option; the scope is the documented multi-format reader and does not claim editing, OCR or conversion

Convert Browse all convert tools

converting documents with SumatraPDF, where the 3.7 pre-release Convert tool documentation documents converting between document formats, images, comics and text: PDF to images and PDF to grayscale, images to PDF, comics to PDF, EPUB to PDF, and text files to PDF, with command-line options and output formats selected by extension; the scope records the documented conversion directions as a pre-release command-line tool, notes that conversion is not present in the current stable 3.6.1 build, and makes no fidelity guarantee

Compress Browse all compress tools

compressing PDFs with SumatraPDF, where the 3.7 pre-release compression documentation documents reducing PDF file size by cleaning, recompressing images and removing or rewriting document data through the compress command and options, and a corresponding GUI path; the scope records the documented pre-release compression capability rather than a stable 3.6.1 one and makes no lossless or specific size-reduction guarantee

Merge Browse all merge tools

merging PDFs with SumatraPDF, where the 3.7 pre-release merge tool and Merge PDF window documentation documents merging pages from multiple files, choosing the input files and page ranges and writing a combined PDF, including the command-line merge tool; the scope records the documented merge operation as a 3.7 pre-release capability rather than a current stable 3.6.1 one, and makes no claim about preserving signatures, forms, links or annotations across a merge

Edit Browse all edit tools

editing annotations with SumatraPDF, where the Editing annotations documentation says annotations, highlights, notes, stamps, images and ink can be added, changed and saved back to PDF files from the context menu, keyboard or Edit PDF toolbar, and that this is available in version 3.3 or later in the current stable line, while the 3.7 pre-release adds signature-image stamping and predefined text snippets; the scope covers annotation and markup editing of PDFs, not rewriting existing body text, and keeps the 3.3-plus boundary

Protect Browse all protect tools

protecting PDFs with SumatraPDF, where the 3.7 pre-release encryption documentation documents encrypting a PDF with a password and decrypting a protected PDF, with the command-line encrypt and decrypt tools and a GUI path; the scope records the documented pre-release AES password protection and decryption capability rather than a stable 3.6.1 one, and makes no reader-enforcement, permission or key-management guarantee beyond the documented password operation

Sign Browse all sign tools

signing PDFs with SumatraPDF, where the 3.7 pre-release signing documentation documents digitally signing a PDF with a certificate from the Windows certificate store or from a PFX/P12 file, including the command-line sign tool, with a visual signature appearance and PKCS#7 signature; the scope records the documented pre-release certificate-based signing capability rather than a stable 3.6.1 one and makes no certificate-authority, trust-validation, timestamping or independent legal-validity guarantee

Where your files are processed

No server involved

A local Windows application with no cloud service. One caveat worth keeping: the pre-release AI chat sidebar hands document context to a third-party agent tool, though not to SumatraPDF servers.

A local Windows application with no cloud service. One exception comes from the pre-release AI chat sidebar: the developers state SumatraPDF does not send your files to its own servers, but the feature does hand document context to whichever third-party agent tool the user has installed, such as Claude Code or OpenAI Codex.

What it does

SumatraPDF is a small, fast, open-source Windows reader for PDF, EPUB, MOBI, comic archives, DjVu, XPS, CHM and images, with a portable build that runs from a USB stick without installation. The current stable release is 3.6.1; annotations, highlights, notes, stamps, images and ink have been supported since 3.3 and can be saved back to the PDF.

A 3.7 pre-release adds a documented set of command-line and GUI tools for merging, splitting, compressing, converting, extracting, redacting, password encryption and certificate-based digital signing. There is no OCR and no cloud service, although the AI chat sidebar sends document context to a network service.

Best for

Windows users who want a very fast, ad-free reader for large or unusual documents, and who are comfortable with a command line for occasional PDF surgery.

Worth knowing

Windows only, with native Windows 7, 8, 10 and 11 builds for 32-bit, 64-bit and ARM64 and a portable option; macOS, Linux and Android are explicitly ruled out, and there is no OCR. The more advanced modification tools are documented for the 3.7 pre-release rather than the current stable 3.6.1 build: the command-line tools for merge, split, compress, convert, extract, encrypt/decrypt, sign and redact are pre-release features, so a stable-reader user should not expect them automatically.

Redaction there is vendor-documented applied removal in the pre-release and has not been independently tested, so it is recorded as unverified rather than as a product-wide removal claim. Certificate signing is a 3.7 pre-release CLI feature using certificates from the Windows certificate store or PFX/P12 files, with no certificate-authority, trust-validation or timestamping guarantee.

Annotations are long-standing stable features and are not the same as editing body text. Reading and processing are local, but the optional AI chat sidebar deliberately sends document context to a third-party network service, so the local-processing claim is conditional for that one feature.

The project is maintained by an individual, Krzysztof Kowalczyk, with no corporate legal entity beyond the maintainer and the SumatraPDF Project Authors; the licence is GPLv3 with BSD-licensed components and bundled third-party notices.

Details, and where each comes from

Vendor statements, our own reading of their pages, and the things nobody has established yet, each answered separately. Where we have not confirmed something it says so rather than guessing, and a row nobody has established is greyed out.

Versions covered
Windows
Website
sumatrapdfreader.org
Requires an account
No
Watermark on the free tier
No
Maximum file size
Not verified
Batch processing
Not verified
Data residency
Self-hosted
Open source
Yes
Self-hostable
Yes
Licence
GPL-3.0, with some code under BSD.

GPL-3.0, with some code under BSD. The repository COPYING file is the full GNU GPL version 3 text, COPYING.BSD covers BSD-licensed components, and the README describes SumatraPDF as a multi-format reader for Windows under the (A)GPLv3 license with some code under the BSD license (see AUTHORS) and names the SumatraPDF Project Authors rather than a company.

GitHub metadata reports GPL-3.0. Bundled third-party components carry their own licences and notices.

There is no corporate legal entity behind the project beyond the individual maintainer and project authors, and the software is free and open source with no ads, bundled software or subscription.

Redaction
Not determined
Programmatic access
None
Last availability check
Responded in 506 ms 21 October 2026

Checked automatically by our own runner, not reported by the vendor. 100% of our last 30 checks got a response.

Why we have not determined this

What that does not establish

The vendor documents an applied redaction tool in the 3.7 pre-release rather than the current stable 3.6.1 build, and this audit did not test the output. The verdict is therefore not a product-wide removal claim: stable users do not have it, and what the pre-release does to the underlying content has not been checked here.

The merge and compression tools carry the same version restriction.

https://www.sumatrapdfreader.org/docs/Redact-a-PDF

What the vendor says

Claims are labelled rather than repeated as fact. Where we have checked something ourselves, it says so and shows when. Checked means we read the vendor's own page and it says what we recorded - not that we tested the behaviour, unless the note says we did.

  • “Free and open source - no ads, no bundled software, no subscription”

    Checked by us - the source says this Read 22 September 2026

    Confirmed verbatim: the line appears unaltered on the page, and the page's own FAQ repeats the substance independently - "Yes. Sumatra PDF is completely free and open source, with no ads or bundled software." Three of the four parts of the claim are therefore asserted twice on the same page, and the fourth, "no subscription", is implicit in a free product rather than stated.

    The page's framing is a comparison with commercial readers - "does everything a closed-source and/or commercial product does, but better in every way" - which is the vendor's assessment rather than a checkable claim. Recorded as the project's description; no control was run.

    Standing: Re-read: the text is unchanged, but the page publishes values that move

    Check it yourself: the source, the SHA-256, and how we checked
    Read
    https://www.sumatrapdfreader.org/free-pdf-reader
    From
    the text a browser renders
    SHA-256
    61d999e1450ecee7c72917bdea8d60418f50955b127cfd67ae6be0d92892ee09

    How we checked

    Re-verified verbatim on 2026-09-22: https://www.sumatrapdfreader.org/free-pdf-reader re-rendered in headless Chrome with scripts/render-page.mjs and the claim's wording found in the rendered text. Originally verified on 2026-09-21. sourceHash is the SHA-256 of the re-rendered text, held as rv-www-sumatrapdfreader-org-free-pdf-reader-8c5e51ef.txt.

    What this hash proves, and what it does not

Each claim is quoted from the vendor's own pages. This section describes what we have and have not checked - it is not a judgement about anyone.

Sponsorship is distribution, not an endorsement or a promise of search rankings, AI citations, traffic, or sales. This listing is a free entry, compiled from published sources.

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Related reading

How this record was put together

Editorial review.
No editor has signed this record off. That is not the same as nothing having been checked, and the lines below say what has.
Source reading.
1 claim taken from the vendor's own pages, read between 22 September 2026 and 22 September 2026.
Website availability.
The vendor's site was last checked on 21 October 2026.
Behaviour testing.
We ran this ourselves. The file handling was watched directly.

Sources: sumatrapdfreader.org (free-pdf-reader, documentation, version history, why-only-Windows, editing-annotations, AI chat, encrypt tool page); repository COPYING file. Licence from the repository.