Free and open-source PDF editor for Windows. View, annotate, OCR, merge, split, edit text, draw, sign, fill forms, print, flatten, and open password-protected PDFs without an Adobe subscription or a phone-home. Install or run portable. Single Windows EXE, ~16 MB, no runtime install required.

Full how-tos live on the help page; internals, formats, and limits on the technical page.

Features

• High-quality PDFium rendering with four view modes (Single, Continuous, Two-Page with a book layout option, Grid), tabbed documents, and a split pane for two documents side by side
• Annotate: inline text editing with font matching, word-wrapping text boxes, draw, lines, highlights (saved with the Multiply blend so text underneath stays readable), images, and page-number / watermark stamps - all with per-tab undo and redo
• Built-in OCR (Tesseract bundled, no cloud): make searchable PDFs, OCR a page or region to the clipboard, extract all text; extra languages download on demand
• Organize pages: merge, split, insert, rotate, crop, extract, delete, drag-and-drop reordering; drop a folder or .zip onto the window to merge its contents
• Transform: rotate, scale, flip, deskew by drawing a level line, perspective correction for photographed pages, and a LEVELS section (black point, white point, midtones) for pale scans
• Forms: fill text, checkbox, radio, and comb fields as live controls and save back; digital signatures with a cloud certificate (Certum SimplySign), plus drawn or imported signatures and initials
• Print with a real in-app preview, paper size and source selection, scale / position / margins / pages-per-sheet options at 300 DPI; Save Flattened rasterizes to a fully uneditable PDF
• Full-text search with highlighting, and column-aware text selection that copies multi-column pages in reading order
• Night-mode invert (per pane in split view), thirteen themes - four of them (Dark, Light, Black and 98SE) with six live accent colors each, 33 looks in all - toolbar styles, and a resizable sidebar that docks left or right
• Localized UI in 11 languages (contribute via TRANSLATING.md); full keyboard shortcut overlay on F1 with list and visual keyboard views
• Opens password-protected PDFs (prompts instead of erroring) and repairs damaged ones
• Runs portable, or self-installs per-user (no UAC) or machine-wide (/silent for scripted deployment); registers as a PDF handler and uninstalls cleanly
• Standards-safe saves: every release is validated with veraPDF across a 2,900-file conformance corpus with a zero-regressions bar - see validation/RESULTS.md
• Local-only: no account, no telemetry, no phone-home

Command line

Every core operation also runs headless from a terminal, with meaningful exit codes, even while the app is open:

KillerPDF.exe --merge out.pdf a.pdf b.pdf scan.jpg
KillerPDF.exe --extract-pages in.pdf 1-3,5 out.pdf
KillerPDF.exe --split in.pdf pages\
KillerPDF.exe --decrypt locked.pdf open.pdf [--password p]
KillerPDF.exe --to-image in.pdf imgs\ --dpi 300 --format jpg
KillerPDF.exe --flatten in.pdf flat.pdf
KillerPDF.exe --print in.pdf --printer "HP LaserJet" --pages 1-4 --copies 2
KillerPDF.exe --ocr scan.pdf searchable.pdf --lang eng
KillerPDF.exe --batch-resave inDir\ outDir\ --log report.csv
KillerPDF.exe --help

Full reference on the help page.

Screenshots

Grid view — Scan a whole document at once while thumbnails and navigation stay close at hand.	Split panes and outlines — Browse two independent documents side by side, with tabs, pages, zoom, and navigation kept per pane.
Night mode and localization — Per-pane inversion, themed context menus, and an interface translated into eleven languages.	Annotation tools — Draw, highlight, add shapes, and choose exact colors without leaving the document.

Requirements

• Windows 10 or 11 (x64)
• No runtime install. Everything needed is inside the EXE (targets .NET Framework 4.8, which ships with every supported Windows release).

Download

WinGet:

winget install killerpdf

Chocolately:

choco install killerpdf

• Prebuilt binary: https://github.com/SteveTheKiller/KillerPDF/releases/latest/download/KillerPDF.exe
• Source (GPL3 corresponding source for this release): https://github.com/SteveTheKiller/KillerPDF/releases/download/v1.7.3/KillerPDF-1.7.3-src.zip

Build from source

git clone https://github.com/SteveTheKiller/KillerPDF.git
cd KillerPDF
dotnet publish -c Release

Output lands in bin/Release/net48/publish/. The publish step produces a single Costura-bundled KillerPDF.exe plus a versioned KillerPDF-<version>-src.zip for GPL3 source distribution.

Requires the .NET 8 SDK or later to build (even though the output targets .NET Framework 4.8).

The PDF write engine (PdfSharpCore, MIT) is vendored under third_party/PdfSharpCore/ and builds as part of the solution; it carries six standards-conformance patches, each marked KillerPDF patch in the source. Origin commit and details are recorded in third_party/PdfSharpCore/VENDORED.txt.

Translations

UI strings live in Strings/ (one XAML ResourceDictionary per locale). To add or improve a language, see TRANSLATING.md. Missing keys fall back to English, so a partial translation is fine.

Changelog

See CHANGELOG.md.

License

GPLv3. See LICENSE. If you fork, modify, or redistribute KillerPDF, your version must also be released under GPLv3 with source available. No exceptions for commercial rebrands.