FreePDF — free, private PDF editor

Fill forms, add text, tick boxes, draw shapes and sign PDFs in the browser. Everything runs on the user's device: files are never uploaded, so hosting is a plain static site (free on Vercel) with no server, storage, or per-use cost.

Features

Area	What you get
Fillable forms	Detects AcroForm fields (text, multiline, checkbox, radio, dropdown) and fills them natively. Optional "Flatten form" on download.
Text	Click anywhere to type. 5 fonts across categories: Helvetica (sans), Times (serif), Courier (mono), Kalam (handwriting), Dancing Script (script). Size, bold, italic, colour. Date stamp.
Form marks	Tick ✓, cross ✗ and radio dot ● for printed (non-fillable) forms. Resizable, recolourable.
Shapes	Box, circle/ellipse, line, arrow — stroke colour, stroke width, fill on/off, fill colour, opacity. Shift = square / circle / 45° snap.
Markup	Freehand pen, highlighter (multiply blend), whiteout.
Images	Insert PNG / JPEG / WebP / GIF.
Signatures & initials	Draw, type (4 signature fonts) or upload (with white-background removal). Black / blue / red ink. Saved on the device for reuse.
Editing	Move, resize, duplicate, bring to front / send to back, delete, undo / redo, arrow-key nudge, zoom.
Robustness	Handles rotated pages, crop-box offsets, and pages whose content leaks graphics state. Password-protected PDFs open after entering the password; encrypted PDFs export as a flattened copy.

Keyboard: V select · T text · D date · K tick · X cross · O dot · R box · E circle · L line · A arrow · P draw · H highlight · W whiteout · I image · S sign · N initials · Ctrl/⌘+Z undo · Ctrl/⌘+Shift+Z redo · Ctrl/⌘+D duplicate · Ctrl/⌘+S download · Del delete · Esc cancel.

How it compares (research summary)

Sejda and Smallpdf are the reference products. Their most-used editing features are the same small set: add text, fill form fields, checkmarks, shapes/whiteout, highlight and draw, images, and signatures (type / draw / upload) plus initials and dates. Both process files on their servers and cap free use (Sejda: 3 tasks per hour, 50 pages, 50 MB; Smallpdf: limited free tasks, and editing the PDF's original text requires Pro).

FreePDF covers that core set with no limits, because the work happens locally in the browser. Not included (yet): editing text that's already in the PDF, adding links or new form fields, and page tools (merge/split/rotate/reorder).

Architecture

• Rendering: pdf.js draws each page to a canvas (lazily, as you scroll).
• Editing layer: plain DOM/SVG overlay per page. Annotations are stored in PDF points with a top-left origin, so zoom is just a CSS transform.
• Export: pdf-lib writes the edits into the original PDF as vector content (text stays selectable, shapes stay sharp). A single transformation matrix maps the on-screen coordinate space into each page's user space, which is what makes rotated/cropped pages work.
• Fast first load: the landing page ships ~17 KB of script (gzipped). The PDF engines (pdf.js, pdf-lib) are separate chunks fetched only when someone opens a file, and signature-only fonts load when the dialog opens.
• Shared geometry: src/shapes.js produces the SVG path for each shape; the same path is drawn on screen and written to the PDF, so output matches what you see.

src/
  main.js       app shell: toolbar, property bar, shortcuts, open/download
  viewer.js     pdf.js loading, page rendering, form-field detection
  overlay.js    annotation rendering, selection, drag/resize, tools, form inputs
  exporter.js   pdf-lib export (+ flattened fallback for encrypted files)
  shapes.js     geometry shared by screen and export
  signature.js  signature/initials dialog
  fonts.js      font registry and text metrics
  state.js      state + undo/redo
  sample.js     generates the demo form

Notes on fonts

pdf-lib's font subsetter drops glyphs from many fonts (Kalam, Caveat). Fonts are therefore embedded whole unless subsetting is known to work for that file (Dancing Script, which can't be embedded whole). The subset flag lives on each font in src/fonts.js. If you add a font, check the exported PDF in a second viewer (e.g. Preview or Chrome).

The three standard fonts only cover Western European characters. Other characters are replaced with ? in the exported file. Arabic/Urdu etc. would need an embedded Unicode font.

Develop

npm install
npm run dev

Before you go live

npm run build      # production build into dist/
npm run preview    # serves dist/ on localhost with the same security headers as Vercel

vercel.json sets a strict Content-Security-Policy (everything from the same origin, no third-party requests), HSTS, no-referrer, clickjacking protection, and long-lived caching for hashed assets. npm run preview applies the same headers, so a policy change that breaks the app shows up locally. If you add a CDN, analytics or an embedded iframe, update the policy in vercel.json first.

Day-to-day workflow: branch, review live, merge

main is the live website. Never work on it directly. Every other branch gets its own private preview link from Vercel, so you can review changes on a real URL before they go live.

git switch -c short-name-of-change     # 1. new branch from main
npm run dev                            # 2. build and test locally
git add -A && git commit -m "What I changed"
git push                               # 3. publish the branch (first push sets up tracking)

以上為 README 的開頭部分。其餘內容請閱讀原文。 檢視完整 README ↗