Best Open Source PDF Desktop Software — Free & Private

If you’ve ever installed a “free” PDF editor only to discover it watermarks every document, nags you to upgrade, or silently phones home with usage telemetry — you already know why open source matters. Most commercial PDF tools treat free users as leads, not customers. Open source PDF software flips that model entirely: the code is public, there are no hidden paywalls, and your files never leave your machine unless you decide they should.

We spent three weeks testing six of the most popular open source PDF desktop tools across Windows 10, macOS Sonoma, and Ubuntu 24.04. We evaluated them on real-world tasks — editing invoices, merging 50-page reports, annotating research papers, and exporting print-ready layouts. Here’s what actually works, what falls short, and which tools we’d recommend to our own team.

What Makes Open Source PDF Software Different?

Three things separate genuinely open source PDF tools from the “free tier” of commercial products:

Full auditability. Every line of code is publicly available on GitHub or a project-hosting platform. Security researchers, independent developers, and curious users can inspect exactly what the software does with your files, your network connection, and your system resources. When a CVE is disclosed for a dependency, you can verify whether the project has patched it — instead of trusting a vendor’s changelog.

Zero telemetry by default. Open source PDF tools don’t need to monetize your usage data because they aren’t built around a freemium funnel. We monitored network traffic during our tests with Wireshark. LibreOffice Draw, PDFsam Basic, and Okular made zero outbound connections during normal operation. No analytics pings, no license check-ins, no crash reporters phoning home.

Community-driven patches. When Adobe Acrobat ships a feature you dislike, your only option is to submit a support ticket and wait. When an open source tool has a bug or a missing feature, you can file an issue, contribute a pull request, or fork the project. We found that critical bugs in popular open source PDF tools are typically patched within days, not quarters.

These advantages matter most if you handle sensitive documents — legal contracts, medical records, financial statements — where privacy isn’t optional. But even for everyday use, the absence of upgrade nags, watermarks, and artificial file-size limits makes open source tools genuinely more pleasant to work with.

Top 6 Open Source PDF Desktop Tools Compared

We narrowed the field from over 20 candidates to six tools that meet our baseline criteria: active development (commits within the last 12 months), cross-platform support for at least two operating systems, and genuine open source licensing (no “source available” tricks).

All six tools are free to download and use indefinitely. None require account creation, and all support full offline operation. If you’re looking for a Best Free Offline PDF Editor for PC, any of the top three picks above will serve you well.

#1 Pick: LibreOffice Draw — Best Overall Open Source PDF Editor

LibreOffice Draw is the hidden gem of the LibreOffice suite. Most users associate LibreOffice with Writer and Calc, but Draw has a powerful PDF import engine that converts each page into an editable vector canvas. In our tests, it handled multi-column layouts, embedded fonts, and complex tables better than any other open source tool we tried.

We tested Draw 24.8.2 against a 42-page financial report with mixed content — tables, charts, vector graphics, and body text. Draw imported all 42 pages in under 8 seconds on our test machine (Intel i7-12700, 16 GB RAM). Text was selectable and editable across every page. Table structures were preserved with minor column-width deviations on two pages. Vector graphics retained their anchor points and could be ungrouped and modified individually.

Installation size: ~1.2 GB for the full LibreOffice suite (Draw is included). If you only need Draw, the Windows installer lets you deselect other components, bringing the footprint down to roughly 450 MB.

Pros

• Deep editing capability. Unlike most PDF tools that only let you add annotations on top of existing content, Draw decomposes the PDF into editable objects. You can change text, recolor shapes, delete elements, and reposition anything on the page.
• Lossless round-trip. Export back to PDF preserves vector quality. We ran a round-trip test (PDF → Draw → PDF) and the output was visually identical to the original at 100% zoom.
• Batch processing via macro. Draw supports LibreOffice Basic macros, so you can automate repetitive tasks like extracting pages or applying watermarks across multiple documents.
• Cross-platform parity. The Windows, macOS, and Linux versions share the same rendering engine. We didn’t encounter any platform-specific layout differences during testing.

Cons

• Large install footprint. At 450 MB minimum, Draw is heavier than dedicated PDF viewers. If you only need to read PDFs, check out our guide to the Best Lightweight PDF Reader for Low-End PC.
• No real-time collaboration. Draw is a single-user, offline application. There’s no built-in sharing or commenting workflow like Google Docs or Acrobat’s cloud review.
• Occasional font substitution. If the original PDF uses fonts not installed on your system, Draw substitutes a similar font. The visual difference is usually minor, but it can matter for brand-critical documents.
• Not ideal for form filling. Interactive PDF forms with JavaScript validation aren’t fully supported. For form-heavy workflows, Okular handles XFA and AcroForm fields better.

#2 Pick: PDFsam Basic — Best for PDF Merge & Split

PDFsam (PDF Split and Merge) Basic does exactly what its name suggests, and it does it reliably. We tested version 5.2.2 and merged 23 separate PDF files (totaling 340 pages) into a single document in 4 seconds. Splitting a 500-page PDF into individual chapter files took under 3 seconds.

PDFsam’s interface is straightforward: a drag-and-drop workspace where you add files, choose an operation (merge, split, extract, rotate, or alternate mix), configure options, and hit Run. There are no toolbars cluttered with features you’ll never use.

Installation size: ~120 MB on Windows, includes a bundled JRE so you don’t need Java installed separately.

Pros

• Blazing fast. Merge and split operations are near-instant for documents under 1,000 pages. We tested with a 2,000-page PDF and it completed in under 12 seconds.
• Simple, focused UI. No learning curve. Anyone who can drag a file into a window can use PDFsam Basic.
• Portable option available. PDFsam offers a portable ZIP that runs from a USB drive — no installation required. Great for regulated environments where you can’t install software.
• Visual merge preview. Before merging, you can see thumbnails of each file and reorder them by dragging.

Cons

• Merge and split only. PDFsam Basic doesn’t edit PDF content. You can’t change text, add annotations, or modify images. (The paid “Enhanced” version adds some of these features, but we’re evaluating the open source Basic edition.)
• Requires Java on Linux. The Linux build doesn’t bundle a JRE, so you’ll need OpenJDK 17+ installed. The Windows and macOS builds handle this automatically.
• No OCR. If you need to make scanned documents searchable, PDFsam won’t help. Pair it with Tesseract OCR or a tool like OCRmyPDF for scanned content.

For dedicated merge and split workflows, PDFsam Basic is unmatched among open source options. See our full comparison in Best Free PDF Merge & Split Software Offline.

#3 Pick: Okular — Best for Reading & Annotating

Okular is the KDE project’s universal document viewer, and it handles PDF annotation better than any other open source tool we tested. Version 24.12 supports pop-up notes, inline highlights, freehand drawing, geometric shapes, stamps, and typewriter text — all stored in standard PDF annotation format so other readers (including Adobe Acrobat) can display them.

We annotated a 60-page research paper with highlights on 18 pages, pop-up notes on 7 pages, and freehand markup on 3 figures. Every annotation was preserved when we opened the file in Adobe Acrobat Reader on a separate machine.

Installation size: ~80 MB on Windows, ~45 MB on Linux (via package manager).

Pros

• Rich annotation toolkit. Highlight, underline, strikeout, freehand draw, geometric shapes, stamps, and file attachments. This is the closest open source equivalent to Acrobat’s commenting features.
• Form filling support. Okular handles both AcroForm and basic XFA form fields. We tested with IRS W-4 forms and tax documents — all interactive fields worked correctly.
• Tabbed interface. Open multiple PDFs in tabs, similar to a web browser. Each tab maintains independent zoom, scroll position, and sidebar state.
• Lightweight. At 80 MB, Okular uses roughly 120–180 MB of RAM with a typical document open. Significantly lighter than LibreOffice Draw for read-only tasks.

Cons

• No PDF editing. You can annotate, but you can’t modify the underlying content — no text editing, no image replacement, no page layout changes.
• Windows build can feel unpolished. Okular was designed for KDE Plasma on Linux. The Windows port works, but some dialog boxes don’t follow native Windows UI conventions, and high-DPI scaling can be inconsistent on multi-monitor setups.
• Occasional rendering glitches. Two of our test PDFs (complex vector diagrams with embedded CID fonts) displayed minor glyph substitution. This is a known upstream Poppler issue and not specific to Okular.

Open Source vs Freeware: What’s the Difference?

This distinction trips up a lot of people, so let’s be precise:

Open source software has its source code publicly available under a recognized license (GPL, MIT, MPL, etc.). You can inspect it, modify it, redistribute it, and — in most cases — use it commercially without paying. The six tools in this article are all genuinely open source.

Freeware is software you can use without paying, but the source code is proprietary. You’re trusting the developer’s claims about what the software does. Many “free PDF editors” fall into this category — Sejda’s free tier, PDF24’s desktop tool, and others. They may be good products, but you cannot verify that they aren’t collecting data, and their free tiers often impose limits (file size caps, page count restrictions, watermarking).

Here’s a practical comparison:

If your priority is privacy and long-term availability, open source wins decisively. If you need a specific commercial feature (like OCR with language packs, or real-time cloud collaboration), some freemium products may justify the trade-off — but read their privacy policies carefully.

How to Get Started with LibreOffice Draw

Here’s a step-by-step guide to installing and using LibreOffice Draw for PDF editing, based on our testing across all three major platforms.

Step 1: Download

Visit libreoffice.org/download and select your operating system. As of this writing, version 24.8.2 is the latest stable release. The download size is approximately 350 MB for Windows, 390 MB for macOS, and 320 MB for Linux (DEB package).

Step 2: Install

Windows: Run the .msi installer. On the component selection screen, expand “LibreOffice” and uncheck Writer, Calc, Impress, Base, and Math if you only want Draw. Click Install. The process takes roughly 90 seconds on an SSD.

macOS: Open the .dmg file and drag LibreOffice into your Applications folder. On first launch, macOS will prompt you to confirm you downloaded the app from the internet — this is normal for unsigned or independently-signed applications.

Linux: On Ubuntu/Debian, run sudo apt install libreoffice-draw. On Fedora, run sudo dnf install libreoffice-draw. On Arch Linux, run sudo pacman -S libreoffice-still. Most package managers install Draw as part of the full suite by default.

Step 3: Open a PDF

Launch LibreOffice Draw, then go to File → Open (or press Ctrl+O). Select your PDF file. Draw will import each page and display them in a page pane on the left side. Click any page thumbnail to jump to it.

Step 4: Edit

Click directly on any text element to select it. You’ll see a bounding box with resize handles. Double-click to enter text-edit mode, where you can change the wording, font, size, and color. Click on shapes, images, or other objects to select, move, resize, or delete them.

Step 5: Export

Go to File → Export As → Export as PDF (or press Ctrl+Shift+E). The export dialog lets you set page range, image compression, and PDF version compatibility. Click Export to save your edited PDF.

Pro Tips

• Use “Select” tool (the arrow icon) instead of the text cursor for repositioning elements. The text cursor is for editing content in place.
• Group related objects by selecting multiple items (Shift+Click) and pressing Ctrl+G. This keeps complex layouts intact when you move them.
• Save as ODF before exporting. Go to File → Save As and save an .odg copy of your work. If you need to re-edit later, opening the ODF file preserves more editability than re-importing the exported PDF.
• Check font embedding. In the PDF export dialog, go to the “General” tab and ensure “Embed fonts” is checked to avoid font substitution issues on other machines.

Frequently Asked Questions

Is open source PDF software safe for business use?

Yes. Tools like LibreOffice Draw and PDFsam Basic are used in government agencies, universities, and enterprises worldwide. Their code is publicly audited, and vulnerabilities are typically disclosed and patched faster than in proprietary software. The MPL 2.0 license (LibreOffice) and AGPLv3 license (PDFsam) both permit commercial use. However, check with your organization’s IT policy — some regulated industries have specific software approval processes.

Can open source PDF editors handle password-protected files?

It depends on the tool. LibreOffice Draw can open password-protected PDFs if you have the password. PDFsam Basic can merge and split encrypted PDFs after entering the correct password. Okular supports encrypted PDFs with full annotation capability. None of these tools can crack or remove unknown passwords — and that’s a feature, not a bug.

Which open source PDF tool is best for filling forms?

Okular is our top recommendation for PDF form filling. It supports standard AcroForm fields (text inputs, checkboxes, radio buttons, dropdown menus) and preserves entered data when you save the file. LibreOffice Draw can interact with some form fields but doesn’t reliably save form data back to PDF format. For complex XFA-based forms (used in some government documents), support varies across all tools — including commercial ones.

Do I need to install the entire LibreOffice suite to use Draw?

Not necessarily. On Windows, the installer lets you deselect individual applications and install only Draw, reducing the footprint from ~1.2 GB to ~450 MB. On macOS, the download is a single monolithic app. On Linux, some distributions offer libreoffice-draw as a separate package, but it typically pulls in shared libraries from the full suite. If disk space is a concern, Okular (80 MB) or Evince (30 MB) are lighter alternatives for reading and annotating.

Can open source PDF tools replace Adobe Acrobat?

For most users, yes — with caveats. LibreOffice Draw handles editing, PDFsam handles merge/split, Okular handles annotation and forms, and Scribus handles professional print layout. Together, they cover perhaps 85% of what Acrobat does. The remaining 15% includes Acrobat-specific features like advanced Preflight profiles, automated accessibility checking (though PAC 2024 is open source), and seamless cloud document workflows. If you need those features specifically, Acrobat may still be necessary. But for editing, merging, annotating, and converting PDFs, the open source stack is genuinely capable.

How do open source PDF tools handle large files?

In our testing, all six tools handled files up to 500 pages without issues. LibreOffice Draw imported a 2,000-page PDF in about 15 seconds and remained responsive (memory usage peaked at ~1.8 GB). PDFsam Basic merged 50 files totaling 3,000 pages in under 8 seconds. Okular opened a 1,500-page technical manual and maintained smooth scrolling with page-level lazy loading. Evince is the lightest option — it loaded a 4,000-page PDF in under 2 seconds by rendering pages on demand rather than loading the entire file into memory.