Annotate PDF
Add visual annotations to PDF documents for review, study, or collaboration. Highlight important text, underline key passages, add strikethrough for deletions, draw freehand marks, or place note pins with comments. All annotations are flattened into the PDF content, making them visible in any PDF viewer.
What does this tool do?
The Annotate tool provides drawing and markup capabilities directly on PDF pages. It supports multiple annotation types: highlighting for emphasizing important text, underlining for key points, strikethrough for indicating deletions, freehand drawing for custom marks and signatures, and note pins for adding comment markers. Choose from six colors to categorize your annotations. Each annotation is drawn directly onto the page content, making it a permanent part of the document.
How it works
Using an interactive canvas interface, the tool renders each PDF page for annotation. As you draw highlights, lines, or freehand marks, these are recorded as vector graphics operations. The undo feature tracks each action for easy correction. When you save, MuPDF applies these graphics as permanent content on each page, flattening them into the page's content stream. The result is a standard PDF that displays your annotations in any viewer without requiring special annotation support.
Features
- Five annotation types: highlight, underline, strikethrough, freehand draw, note pin
- Six color choices for categorizing annotations
- Per-page undo to correct mistakes
- Annotations flattened into page content (visible in any viewer)
- Works on any number of pages in the document
- Precise drawing with mouse or touch input
- Zoom for detailed annotation work
How to use
- 1
Upload your PDF
Drag the PDF you want to annotate onto the drop zone. The tool loads the document and displays the first page in the annotation viewer.
- 2
Select annotation tool
Choose from the toolbar: Highlighter for text emphasis, Underline for key points, Strikethrough for deletions, Draw for freehand marks, or Note for comment pins.
- 3
Mark up the document
Click and drag on the page to add annotations. For text annotations (highlight, underline, strikethrough), drag across the text. For draw, drag freely. For notes, click to place. Use undo if needed.
- 4
Navigate and continue
Use page navigation to move between pages. Add annotations to any or all pages as needed. Each page maintains its own annotation set.
- 5
Save the annotated PDF
Click Save with Annotations. The marked-up PDF downloads with all annotations permanently embedded in the page content.
Common use cases
Review and mark up documents
Add highlight and comment annotations during document review cycles, flagging sections for revision or approval.
Study and research notes
Students and researchers can highlight key passages, add margin notes, and mark important sections in academic papers and textbooks.
Legal document markup
Attorneys can redline contracts with strikethrough deletions and highlight additions for negotiation and revision tracking.
Design feedback
Designers and clients can mark up PDF mockups with annotations indicating changes, corrections, or approval.
Tips & best practices
- Use different colors to categorize annotations — yellow for important, green for approved, red for issues
- Zoom in for precise text highlighting — the annotation tools work at all zoom levels
- Freehand draw is perfect for quick signatures or circling specific areas
- Note pins are great for adding comments without cluttering the page with large text blocks