Best Free & Open Source Alternatives to Foxit Reader

What is PdfDing?

PdfDing is a self-hosted PDF manager, viewer, and editor written in Python (Django) with a Svelte frontend. It is designed to give individuals and small teams a private alternative to cloud PDF services: you run it yourself in Docker, Docker Compose, or Helm, and your documents live on your own infrastructure rather than on a vendor's servers. The name is a nod to linkding, the bookmark manager that inspired the project's tagging and sharing model.

Key features

• In-browser PDF reader that streams pages on demand, remembers the current position, and continues across devices.
• Library organisation via workspaces, collections, multi-level tags, starring, archiving, and progress bars per PDF.
• Editing — add text, highlights, drawings, and signatures; export highlights and comments to Markdown.
• Sharing — share single PDFs or whole collections via a link or QR code, with optional access control lists.
• Auth: local accounts, two-factor authentication (TOTP and WebAuthn), and OIDC single sign-on for organisations.
• Clean dark UI with an inverted colour mode for night reading and keyboard-friendly bulk actions.
• Private by design: no telemetry, no third-party data sharing, no analytics.

Comparison to paid PDF software

PdfDing targets users who currently pay for Adobe Acrobat's cloud tier, Foxit PDF Editor's sharing features, or services like DocSend for distribution and analytics. Because it is self-hosted, the only cost is the server you already operate, and there are no per-user licence fees. The reader, editor, and sharing functionality are deliberately narrower than a desktop PDF editor such as Adobe Acrobat Pro, but they cover the day-to-day workflow of someone reading, highlighting, and signing PDFs across multiple devices, with the same level of polish you would expect from a SaaS PDF tool.

What is SumatraPDF?

SumatraPDF is a free, open-source document reader for Windows built in C and C++. It supports PDF, EPUB, MOBI, FB2, CHM, XPS, DjVu, and comic-book archive formats (CBZ, CBR) in a single small executable that launches in under a second, even on older hardware. The project is intentionally minimal: it does not bundle a cloud service, an account system, OCR, or a ribbon of upsell features common to the commercial PDF readers it competes with.

Key features

• Multi-format: reads PDF, EPUB, MOBI, FB2, CHM, XPS, DjVu, CBZ, and CBR in one app, with per-format settings such as comic-book page view mode for CBZ/CBR.
• Fast and portable: ships as a single small .exe or a portable folder, no installer required, no admin rights needed, no telemetry, no ads.
• Annotations and highlights stored inside the PDF, with optional secondary sidecar .txt annotations.
• Customisable keyboard shortcuts, command-line interface, and a built-in ebook reader mode.
• Built-in PDF tools: re-flow text for tablet-style reading, favorite files and recent folders, full-screen presentation mode, and PostScript and image printing.

Comparison to paid PDF software

SumatraPDF is a lightweight alternative to Adobe Acrobat Reader, Foxit Reader, and Nitro PDF Reader. Where those products bundle cloud storage, account sign-ins, advertisements, toolbars, and large update installers, SumatraPDF is a single self-contained executable that does not phone home. The viewer supports advanced PDF features (links, forms, outlines, encryption) without any of the commercial readers' bloat. A separate companion utility, SumatraPDF Pro (commercial), adds advanced editing, OCR, and conversion, but the core viewer remains free.

What is Koodo Reader?

Koodo Reader is a free, open-source ebook and document reader that runs on Windows, macOS, Linux, Android, iOS, and the Web. It is built with Electron and TypeScript and supports a long tail of formats that includes PDF, EPUB, MOBI, AZW, FB2, DJVU, CBR/CBZ, TXT, Markdown, DOCX, HTML, and RTF. The app is aimed at readers who want one library that follows them across every device they own, without paying for a subscription.

Key features

• Cross-platform parity: the same library, reading progress, highlights, and notes are available on desktop, mobile, and the web app.
• Sync and backup to OneDrive, Google Drive, Dropbox, iCloud, MEGA, pCloud, Yandex Disk, Box, FTP, SFTP, WebDAV, SMB, or any S3-compatible object store.
• AI tools: optional integration with custom AI models for translation, dictionary lookup, summaries, and an in-line encyclopedia, all running against your own keys.
• OPDS catalogue support, plus a browser extension to save articles on the open web straight into your library.
• Plugin ecosystem with 50+ built-in plugins for translation, dictionaries, OCR (Paddle and Tesseract), text-to-speech, and more.
• Library features: bookmarks, notes, highlights exportable to CSV/Markdown/HTML/TXT/PDF, multi-level labels, snapshot/version-control, statistics, and password protection (with biometric unlock on supported devices).

Comparison to paid PDF software

Koodo Reader covers the same ground as Adobe Acrobat, Foxit Reader, PDF Expert, and Calibre (closed-source forks), but does it under an AGPL-3.0 licence with no premium tier and no advertisements. Unlike the paid readers, the mobile and web apps are full citizens of the same library, and cloud sync does not require a vendor account: you point Koodo Reader at any WebDAV or S3 bucket you control. Compared with PDF Expert for iOS or Adobe Acrobat Reader, the AI features are optional and self-hosted by default, the sync layer is end-user configurable, and the entire app remains usable fully offline.

What is Sioyek?

Sioyek is a free, open-source PDF reader designed for power users who work with large documents such as textbooks, academic papers, and technical manuals. It ships native installers for Windows, macOS, and Linux, and is built on top of the MuPDF rendering engine for fast page loading even on hundreds-of-megabytes PDFs.

Key features

• Smart navigation: a Quick Open dialog lets you search every PDF you have previously opened by title or path; a Table of Contents viewer jumps to any section.
• Smart Jump: click on a figure or in-text reference and Sioyek jumps to the referenced item even if the PDF does not contain internal links.
• Marks and bookmarks: vim-style single-character marks (local and global) and named bookmarks for quickly returning to a page.
• Highlights, annotations, and an overview panel that lists all figures, references, and tables in a document.
• Portals: pin two views of a document side-by-side, ideal for multi-monitor reading.
• Port-friendly installer with no telemetry, ads, or required account.

Comparison to paid PDF software

Compared to Adobe Acrobat Reader, Foxit Reader, and Nitro PDF, Sioyek launches far faster, ships a much smaller footprint, and stays out of your way with a keyboard-driven UI inspired by vi. Unlike Adobe Acrobat Reader, which nudges users toward cloud storage and paid features on every launch, Sioyek does not bundle any upsell, nor does it phone home. Its research-focused features (Smart Jump, Overview, bibliography lookup) are unique among free readers and are aimed squarely at students, academics, and engineers.

KillerPDF is a local-only, portable PDF editor for Windows built for field techs and privacy-conscious users. It offers high-quality rendering via PDFium, inline text editing with font matching, annotation tools (highlight, freehand draw, text boxes), digital signatures, merge/split capabilities, and full-text search — all without an Adobe subscription or any phone-home telemetry.

The application is distributed as a single self-installing EXE (~6 MB zipped) that targets .NET Framework 4.8. On first launch it presents an Install or Run dialog; if installed, it goes per-user to %LOCALAPPDATA% with no UAC required, registers as a PDF file handler, adds a Start Menu shortcut, and can self-uninstall cleanly. Password-protected PDFs are supported, with the decrypted copy held in temp for the session.