pdfdelta 0.1.0

Visual diff for born-digital PDFs — highlights changes directly on the original pages

pdfdelta

pdfdelta is a lightweight visual diff tool for born-digital PDFs.

Given an old and a new version of a PDF, it writes highlights directly onto the original pages so revisions are easy to review: deletions on the old file, additions on the new file.

It is mainly designed for academic papers and technical documents, where small wording changes matter and layout is part of the review process.

Features

• Highlights changes directly on the original PDF pages
• Works well for born-digital PDFs such as papers, reports, and drafts
• Handles multi-column layouts better than plain text diff tools
• Tries to reduce noisy highlights from simple reflow
• Keeps the review workflow visual and page-based

Installation

If you are using the repository directly:

pip install git+https://github.com/mli55/pdfdelta.git

Usage

pdfdelta old.pdf new.pdf

This writes two annotated files:

• old_marked.pdf — original pages with deletions highlighted
• new_marked.pdf — revised pages with additions highlighted

Options

Flag	Default	Description
--old-out	old_marked.pdf	Output path for the annotated old PDF
--new-out	new_marked.pdf	Output path for the annotated new PDF
--opacity	0.35	Highlight opacity (0.0–1.0)

How It Works

 old.pdf    new.pdf
   │           │
   ▼           ▼
┌──────────────────┐
│  Extract words   │  PyMuPDF: word text + bounding boxes
└────────┬─────────┘
         ▼
┌──────────────────┐
│  Global diff     │  Flatten all pages → SequenceMatcher
└────────┬─────────┘
         ▼
┌──────────────────┐
│  Word-level diff │  Per-word & sub-word precision
└────────┬─────────┘
         ▼
┌──────────────────┐
│  Reflow filter   │  Suppress cross-page / cross-column noise
└────────┬─────────┘
         ▼
┌──────────────────┐
│  Annotate PDFs   │  Highlights on original pages
└────────┬─────────┘
         ▼
 old_marked.pdf
 new_marked.pdf

License

MIT