MmdPdf is a free, 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. Install it or run it portable from the same Windows download. No runtime installation is required, and the app never phones home.

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 with inline text editing and font matching, word-wrapping text boxes, drawing, lines, highlights, images, and page-number or watermark stamps. Highlights use the Multiply blend so the text underneath stays readable, and every tab has its own undo and redo history.
• 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
• Export one page or a multi-page selection as PNG or JPEG directly from the Pages panel
• 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 inversion works independently in each split pane. Thirteen themes, live accent colors, and toolbar styles provide 33 looks, while the resizable sidebar can dock on either side.
• Localized UI in 12 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 tested against a 2,900-file veraPDF conformance corpus with a zero-regressions requirement. 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:

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

Full reference on the help page.

Screenshots

Grid view and twelve languages - Survey a whole document at once, with the menu bar hidden and the interface switchable between twelve languages.	Split panes and Transform - Work in two independent panes while previewing rotation, scale, flip, skew, perspective, and Levels before applying.
Annotation colors and forms - Draw with exact colors while viewing fillable fields, comb boxes, and the brochure's live form examples.	Image picker and previews - Browse images, inspect a large preview, and return directly to the open 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 mmdpdf

Chocolately:

choco install mmdpdf

• Prebuilt binary: https://github.com/SteveTheKiller/MmdPdf/releases/latest/download/MmdPdf.exe
• Source (GPL3 corresponding source for this release): https://github.com/SteveTheKiller/MmdPdf/releases/download/v1.7.5/MmdPdf-1.7.5-src.zip

Build from source

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

Output lands in bin/Release/net48/publish/. Normal publishing produces the development single-file build plus a versioned MmdPdf-<version>-src.zip. The release pipeline builds a verified multi-file payload and packs it into one portable MmdPdf.exe; installed shortcuts launch the inner app directly for faster startup.

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 MmdPdf 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 MmdPdf, your version must also be released under GPLv3 with source available. No exceptions for commercial rebrands.