How to Annotate a PDF: Comments, Highlights, and Notes (2026)

PDF annotations — highlights, sticky notes, comments, underlines, strikethroughs, drawings — let you mark up a document without altering its underlying content. The original text stays intact; your annotations sit as a separate layer on top. This makes annotations ideal for reviewing drafts, studying documents, and collaborative feedback.

Types of PDF Annotations

Highlight: Colors over text to mark important passages. Standard yellow, but most tools support multiple colors for categorization.

Sticky Note (Comment): A small icon in the margin that expands to show a typed note when clicked. Used for detailed comments, questions, or feedback without cluttering the page.

Text Comment (Callout): A text box with a line pointing to a specific area. More prominent than a sticky note — useful for annotations that should be visible without clicking.

Underline: Draws a line under text — signals importance without the visual weight of highlighting.

Strikethrough: Draws a line through text — signals proposed deletion or questioning the text.

Squiggly underline: Wavy underline — signals a spelling or grammatical question.

Drawing / Freehand: Pen/pencil strokes for circling, arrows, or handwritten notes.

Shape annotation: Rectangles, circles, arrows placed over content to draw attention to specific areas.

Stamp: A pre-made image (APPROVED, DRAFT, CONFIDENTIAL, or custom) placed on a page.

Method 1: Adobe Acrobat Reader (Free, Best Feature Set)

Acrobat Reader has the most complete annotation toolkit without any cost.

Opening the Comment toolbar:

• Right panel: click Comment → the annotation toolbar appears above the document
• Or: View → Tools → Comment → Open

Highlighting:

1. Click the Highlight tool (yellow marker icon)
2. Click and drag over text to highlight it
3. Right-click the highlight → Add Note to Highlight to attach a comment
4. Right-click → Properties to change the highlight color

Adding a sticky note:

1. Click the Add Sticky Note tool (speech bubble icon)
2. Click anywhere on the page to place the note
3. A yellow sticky note opens — type your comment
4. Click outside to close; the note appears as a small icon
5. Click the icon to expand and read or edit

Text markup (underline, strikethrough, squiggly):

1. Select the text tool and highlight the text you want to mark
2. The markup toolbar appears above the selection — choose Underline, Strikethrough, or Squiggly
3. Or use the Text Markup tools in the Comment toolbar first, then select text

Drawing:

1. Comment toolbar → Drawing Markup → Pencil
2. Click and drag to draw freehand on the page
3. Double-click to end a pencil stroke

Shapes and arrows:

1. Comment toolbar → Drawing Markup → Rectangle, Oval, or Arrow
2. Click and drag to place the shape

Saving annotations: Annotations are saved as part of the PDF. File → Save to save with annotations embedded. Recipients who open the PDF in any modern reader will see your annotations.

Viewing all comments: View → Navigation Panels → Comments opens a panel listing every annotation with the author name, date, and content — useful for reviewing all feedback at a glance.

Method 2: Browser (Chrome, Edge, Firefox)

Browsers offer basic highlighting and text selection but limited annotation beyond that.

Chrome/Edge built-in (2025+):

• Select text → a small toolbar appears with Highlight and Note options
• Highlights are saved in the browser session but may not persist in the PDF file itself
• For permanent annotations: use Acrobat Reader or an online editor

For full browser-based annotation: OnlinePDFEdits works in the browser and provides highlight, text comment, and drawing tools with permanent embedding in the downloaded PDF.

Method 3: Mac — Preview

Preview includes solid annotation tools built into macOS.

Opening the markup toolbar:

• View → Show Markup Toolbar
• Or click the toolbar icon (pencil in a circle) in the top bar

Highlighting:

1. Select text by clicking and dragging
2. Click the Highlight button in the Markup toolbar
3. Click the dropdown next to Highlight to choose color or switch to Underline/Strikethrough

Sticky Notes:

1. In the Markup toolbar, click Note (speech bubble icon)
2. Click on the page
3. A note field appears — type your comment
4. Click outside to minimize

Drawing:

1. Markup toolbar → Sketch (pencil icon)
2. Draw freehand
3. Preview auto-smooths rough shapes into recognizable forms

Text box:

1. Markup toolbar → Text (T icon)
2. Click on the page
3. Type your text — functions as a visible text annotation rather than a hidden note

Signatures: Markup toolbar → Signature → Create Signature (trackpad, camera, or iPhone prompt on macOS Sonoma+)

Annotations saved in Preview are PDF-standard and viewable in Acrobat Reader and other PDF viewers.

Method 4: Mobile (iOS and Android)

iOS — Markup (Built-in, No App Needed)

1. In Files, Mail, or Safari: tap the PDF to open it
2. Tap the Markup icon (pen tip in a circle) in the top right
3. Use the toolbar at the bottom:
   • Pen, Highlighter, Pencil: freehand drawing
   • Lasso: select and move existing markup
   • Eraser: remove markup
   • Shapes tool: add arrows, circles, rectangles
   • Text tool: add typed annotations
4. Tap Done — annotations are embedded in the file

Highlighting text specifically (not freehand): Tap and hold text → drag selection handles → tap the Highlight option in the popup menu (may require scrolling the popup).

Android — Adobe Acrobat Reader (Free)

1. Open the PDF in Adobe Acrobat Reader for Android
2. Tap the pencil/comment icon in the bottom toolbar
3. Comment tools appear:
   • Highlight: tap the highlighter, then select text
   • Sticky note: tap the note icon, then tap the page
   • Drawing: tap the pencil icon for freehand
4. Tap the back button when done → tap Save

Third-party options for Android: Xodo PDF Reader has an excellent free annotation suite — draw, highlight, type comments, and stamp. Well-regarded for tablets.

Annotation Best Practices for Review Workflows

Use colors purposefully: Assign meaning to highlight colors before starting a review. Example: Yellow = important, Red = error or question, Green = approved, Blue = reference for later. Note the key at the top of the document or in a cover email.

Add context to highlights: A bare highlight with no note means the reader has to guess why you marked it. Even a single word ("unclear," "check date," "delete?") makes the annotation useful.

Use sticky notes for questions: Don't embed questions in the document text — add them as sticky notes so they're clearly comments and not part of the content.

Name your annotations: In Acrobat, your annotations are attributed to the name in Edit → Preferences → Identity → Name. Set this to your actual name so recipients know who made which comment.

Summarize at the top: For document reviews, add a single sticky note on page 1 summarizing overall status ("reviewed — 3 issues to address before sign-off") so the author knows at a glance what the overall finding is.

Exporting and Sharing Annotated PDFs

Sharing with annotations visible: Just share the PDF file — annotations are embedded. Any reader that supports PDF annotations (Acrobat, Preview, most PDF apps) will display them.

Sharing without annotations (clean copy): To send a version without your markup, "flatten" the annotations:

• Acrobat Pro: Document → Flatten
• Print to PDF: print the annotated PDF to a PDF printer — annotations become part of the page image

Printing with annotations: Acrobat Reader: File → Print → in the Comments and Forms dropdown, select "Document and Markups" to print with annotations, or "Document" to print without.

Exporting a summary of comments: Acrobat Pro: Comment panel → menu → Export to Data File (exports comments as FDF or XFDF for import into another copy of the same PDF) or Print Comments Summary (creates a printable list of all annotations).

FAQ

Can the recipient remove my annotations?

Yes — anyone with Acrobat Pro can delete annotations. PDF annotations are not permanent unless the PDF is flattened (which merges annotations into the page content and makes them uneditable). For permanent markup (like for archival purposes), flatten before sharing.

My highlights disappeared when I re-opened the PDF. Why?

Two common causes: (1) You annotated in a browser and the browser saved the highlights only in session — they weren't embedded in the file. Download the PDF and annotate with Acrobat Reader or Preview instead. (2) You saved in a format that didn't preserve annotations (exported as image, for example). Always save as PDF after annotating.

Can I annotate a PDF that has editing restrictions?

Annotation is sometimes allowed even when editing is restricted. PDF permissions have a separate "Commenting" permission — the document owner can allow comments while blocking text editing. If you try to add a comment and Acrobat blocks it, the document restricts annotations too. You'd need the owner password to change this, or use the browser Print to PDF trick to create an unrestricted copy first.

How do I delete an annotation?

Click the annotation (highlight, sticky note, shape, or drawing) to select it → press Delete or Backspace. In Acrobat, you can also right-click any annotation → Delete. In Preview, click the annotation → press Delete.