pdfdelta 0.1.1

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. It is designed to compare revisions of academic papers and technical documents by highlighting changes directly on the original pages.

The tool generates two annotated files: deletions are marked on the old version, and additions are marked on the new version.

Capabilities

• Works fine with multi-column layouts and complex papers.
• Skips "fake" changes caused by text moving to a new line, paragraph and page breaking.
• Not confused by moving figures, tables, or math formulas.

Installation

pip install pdfdelta

If you want to install directly from the repository:

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)

Features

• Direct Annotation: Highlights changes as native PDF annotations on the original layout.
• Layout Aware: Optimized for multi-column papers and technical reports.
• Noise Reduction: Filters out visual artifacts caused by simple text reflow across lines or pages.
• Structural Support: Better handling of figures and tables.

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