Open. Fix. Save. Done.
A free, open-source, lightweight PDF editor for Windows 11 — built for people who find Acrobat too bloated and complex.
MegaPDF does four things exceptionally well and deliberately nothing else:
- Edit text — click any text in the document and type, like editing a Word file.
- Check boxes — click an empty square and it becomes a checked box.
- Apply signatures — keep a small personal library of signature images; drag one onto the page.
- Save — Save overwrites, Save As creates a copy. No export wizards, no "flatten" dialogs.
No account. No cloud. No subscription. All processing is local.
The full Software Design Document lives in SDD.md — product principles, feature specifications, architecture, and deployment strategy. Read it before contributing; the non-goals list is enforced.
- C# / .NET 8, WinUI 3 (Windows App SDK), CommunityToolkit.Mvvm
- PDFium as the PDF engine, behind an
IPdfEngineadapter, with an in-house interactive text-editing layer - MSIX packaging (Microsoft Store, direct download, winget)
SDD.md Software Design Document (start here)
src/MegaPDF.Core/ Engine adapter, services, edit operations (UI-independent)
src/MegaPDF.App/ WinUI 3 application
tests/MegaPDF.Core.Tests/ Unit tests (engine mocked)
Requires the .NET 8 SDK on Windows 11 (or Windows 10 1809+). No Visual Studio needed.
dotnet build MegaPDF.sln
dotnet test MegaPDF.sln
powershell -File tools\Build-Installer.ps1
This produces a signed, self-contained package under artifacts\MegaPDF.App_<version>_x64_Test\
along with the generated Install.ps1. To install: right-click Install.ps1 → Run with
PowerShell (it trusts the dev certificate — one elevation prompt — then installs). The
installer registers MegaPDF as an available .pdf handler; uninstall cleanly via
Settings → Apps. Store releases will be signed with a real certificate instead (SDD §5).