How to Highlight Text in PDF Documents
Highlight text in PDF: a practical, tested walkthrough. Use different colors, underline, strikethrough, and add comments to your documents.
What This Annotation Guide Covers
This guide was written and tested by James Park, a Legal Document Reviewer with 9 years of hands-on experience in legal documents, annotations, redaction, compliance. James worked as a paralegal for 9 years, where he handled thousands of legal PDFs daily.
Highlighting text in a PDF is the most common annotation task — marking key passages in contracts, flagging important clauses in legal documents, or color-coding sections in research papers. Yet the quality of highlight tools varies enormously: some produce semi-transparent overlays that obscure text, others lack color options, and most free tools cannot flatten highlights for permanent inclusion.
This guide covers four methods for highlighting text in PDFs, from basic single-color highlighting to multi-color categorization systems. We tested each on legal contracts, academic papers, and business reports to evaluate highlight precision and text legibility.
Time to read: 3-4 minutes | Difficulty: Beginner | Last updated: 2026-07-25
Related Annotation Guides
While reading this page, these related guides may save you time:
Marking Up the PDF Step by Step with a Desktop Editor
1 Open the PDF and Select the Highlight Tool
Launch your desktop PDF editor and open the document. Switch to Comment or Annotate mode. Select the Highlight tool from the annotation toolbar. Choose a highlight color — yellow is standard for general use. The cursor changes to a text selection cursor.
2 Select Text and Apply Highlight
Click and drag over the text you want to highlight. Release the mouse button to apply the highlight. The selected text is now overlaid with a semi-transparent color. The highlight appears as an annotation that can be selected, modified, or deleted later.
3 Use Multiple Colors for Categorization
For review workflows, switch colors for different categories: select text, then choose the appropriate color from the highlight color palette. Use keyboard shortcuts if available for fast color switching. Apply consistent color coding throughout the document (e.g., all action items in blue, all concerns in red).
4 Review and Modify Highlights
To change a highlight's color: click on it to select, then choose a new color. To delete: click and press Delete. To add a note to a highlight: right-click and select 'Add Note' or 'Open Comment' — the note appears in the comments panel linked to the highlight.
5 Save, Export Highlights, or Flatten
Save with a new filename. If your editor supports highlight export, generate a summary of all highlighted text. If highlights should be permanent, use Flatten to convert them to content. Verify in a different PDF reader that highlights display correctly and text remains legible beneath them.
📋 Quick Recap of the Annotation Steps
Print this box or keep it open while you work through the tutorial.
- 1Launch your desktop PDF editor and open the document. Switch to Comment or Annotate mode. Select the Highlight tool from the annot…
- 2Click and drag over the text you want to highlight. Release the mouse button to apply the highlight. The selected text is now over…
- 3For review workflows, switch colors for different categories: select text, then choose the appropriate color from the highlight co…
- 4To change a highlight's color: click on it to select, then choose a new color. To delete: click and press Delete. To add a note to…
- 5Save with a new filename. If your editor supports highlight export, generate a summary of all highlighted text. If highlights shou…
Free Ways to Annotate a PDF (and Their Limits)
No desktop editor installed? Here are free alternatives — we list their limitations honestly.
Quick Reference: Highlighting PDF Text
Basic Highlight: Select the Highlight tool (marker icon), then drag over text. Most readers support yellow, green, blue, pink, and orange highlights. Right-click a highlight to change its color or add a note.
Underline / Strikethrough: Alternative to highlight — use Underline for emphasis or Strikethrough to mark text for deletion. Both are annotation types that sit on top of the text without modifying it.
Highlight + Note: Double-click any highlight to attach a sticky note. Your note appears in the comments panel and is searchable. Use this to explain why you highlighted a passage.
Export Highlights: Desktop editors let you export all highlighted text as a summary document (TXT, CSV, or PDF). Highlight key passages across a 100-page document, then export them as a single summary.
Annotation Tools Compared: Free vs. Desktop
We tested each method on real documents to give you an honest comparison.
| Method | Annotate | Precision | Offline | Free |
|---|---|---|---|---|
| Microsoft Edge | Basic | ★★ | ✔ | ✔ |
| macOS Preview | Basic | ★★★ | ✔ | ✔ |
| Adobe Acrobat Reader | Full | ★★★★ | ✔ | ✔ |
| LibreOffice Draw | Full | ★★★ | ✔ | ✔ |
| Desktop Editor | Full | ★★★★★ | ✔ | Trial |
Verdict: Edge and Preview cover basic highlighting. For stamps, measurements, and professional markup, a desktop editor is the clear choice.
Annotating PDFs: Common Questions, Answered
Can I search for specific highlight colors?
Most PDF readers allow you to filter comments by type (Highlight, Underline, Strikethrough) and by author. To find all yellow highlights, sort the comments panel by type and scan for Highlight entries.
How do I remove all highlights from a PDF?
Open the Comments panel (usually a sidebar), select all Highlight annotations (Ctrl+A), and press Delete. Or use 'Remove All Annotations' to clear everything. This does not affect the underlying text.