How to Add Annotations to a PDF

Introduction

Complete guide to PDF annotations: highlights, comments, stamps, and drawing marks. If you're new to this topic, don't worry — this guide walks you through everything step by step with clear explanations and practical examples. Whether you're using PDFly's free online tools or building your own workflow, this guide covers everything you need to know about how to add annotations to a pdf.

Understanding Editing

PDF editing encompasses text modification, image replacement, annotation, page manipulation, and more. Modern PDF editors work directly in the browser, letting you make changes without expensive software. Understanding editing capabilities and limitations helps you choose the right approach for your needs.

Key Concepts You Need to Know

Text editing requires the font to be embedded or available on the system
Annotations are non-destructive — they overlay content without changing the original
Page operations (rotate, delete, reorder) modify the document structure
Flattening converts interactive elements to static content for secure sharing
Redaction permanently removes content — unlike deletion, it cannot be undone

1

Open the PDF Editor

Launch PDFly's Edit PDF tool and upload the document you want to modify.

2

Make Your Edits

Use the toolbar to add text, images, annotations, shapes, or modify existing content as needed.

3

Review Changes

Preview the edited document to ensure all changes are correct and properly positioned.

4

Save and Export

Download the edited PDF. The original file remains unchanged on your device.

Tips & Best Practices

Work on a copy of your original PDF to preserve the unedited version

Use consistent font sizes and styles when adding new text

Flatten annotations before sharing if recipients don't need to edit them

Save frequently when making complex edits to avoid losing work

Use redaction (not just covering) for sensitive information

Common Mistakes to Avoid

Avoid These Common Pitfalls

Editing text in a PDF without embedded fonts may cause font substitution
Covering text with shapes is not redaction — the text is still recoverable
Excessive annotations can slow down PDF rendering
Not flattening forms before distribution allows unwanted modifications
Deleting pages can break internal links and bookmarks

Quality Checklist

0 / 5 completed

A backup copy of the original PDF has been saved All text edits use appropriate fonts and sizes Annotations are correctly positioned and styled Redaction has been applied properly (not just covered) The edited document has been reviewed for accuracy

Key Takeaways

Always work on a copy of your original PDF

Use redaction, not covering, for sensitive information

Flatten annotations and forms before sharing if editing isn't needed

Frequently Asked Questions

Yes, PDFly's Edit PDF tool lets you modify existing text, add new text, replace images, and add annotations. If the PDF's font is embedded, text edits will match the original styling.

Absolutely. All editing happens in your browser — your PDF is never uploaded to a server. This ensures complete privacy for sensitive documents like contracts and medical records.

Yes, PDFly supports highlights, comments, sticky notes, stamps, shapes, and freehand drawing. Annotations can be added without modifying the underlying document content.

Edits are saved to a new copy of the PDF. The original file on your device remains unchanged. You can always start over by re-uploading the original.

How to Add Annotations to a PDF

Introduction

Understanding Editing

Key Concepts You Need to Know