How to Annotate PDF Free - Highlight, Comment & Mark Up Documents
Learn how to annotate PDF files for free. Add highlights, comments, drawings, and sticky notes to your PDFs without expensive software.
Annotating PDFs is essential for reviewing contracts, studying, collaborating on documents, and marking up research papers. You don't need to pay for Adobe Acrobat to do this well. Free options exist across every platform and work reliably for most use cases.
Free PDF Annotation Tools in 2026
The best free annotation options are often already on your device. Let's cover them by platform:
Annotate PDF on Windows
Microsoft Edge: Edge has evolved into a capable PDF reader with solid annotation features. Open any PDF in Edge (just drag it into the browser) and you'll find tools for highlighting text, adding text notes, drawing, and erasing. Everything is saved within the PDF file itself. This is free and requires no installation beyond the browser you already have.
Foxit PDF Reader (Free): One of the best free PDF readers available, Foxit includes highlight, underline, strikethrough, sticky notes, drawing tools, and stamps. The free version covers annotation needs thoroughly. Paid features are for editing and converting.
Annotate PDF on Mac
Preview (Built-in): Mac's Preview app has excellent annotation tools that are easy to overlook. Open a PDF in Preview, click the Markup toolbar button (pencil icon), and you get highlights, text notes, shapes, signatures, and freehand drawing. All free, all built-in.
Access the markup toolbar via View > Show Markup Toolbar. You can add color-coded highlights, sticky notes, arrows, and even your signature. Changes save directly to the PDF file.
Annotate PDF on iPhone and iPad
Apple Files & Markup: On iOS, tap any PDF file and hit the pen icon to enter Markup mode. You get highlighting, free-draw, text boxes, signatures, and shapes. This is ideal for quick annotations but limited for heavy reviewing.
GoodNotes 5 (Paid but popular): For students and power users who annotate heavily, GoodNotes offers a far richer experience. Not free, but the one-time purchase cost is worth it for regular use.
Notability: Another excellent paid option for iPad with a focus on handwriting and annotation. Great for studying and note-taking on top of PDFs.
Annotate PDF on Android
Adobe Acrobat Reader (Free): The free Android app from Adobe provides robust annotation features including highlighting, strikethrough, underline, sticky notes, and freehand drawing. The annotation features in the free tier are genuinely good — you don't need to subscribe just to mark up a PDF.
Xodo PDF Reader: A fully free app with no paid tier. Xodo handles highlights, notes, drawings, stamps, and even supports collaborative real-time annotation with others. Excellent for teams reviewing documents together.
Annotation Types Explained
Highlights: Color-code important text by selecting it and applying a highlight. Use different colors to categorize — yellow for important, blue for questions, green for action items.
Sticky notes: Pop-up comments anchored to a specific point in the document. Best for longer comments that would clutter the page if displayed inline.
Text comments: Inline text that appears directly on the PDF page, visible without clicking. Good for short notes.
Drawings and shapes: Freehand markup, arrows, circles, and rectangles for calling out specific areas of a page. Useful in design reviews and image-heavy documents.
Stamps: Pre-made approval marks like "Approved," "Rejected," or "Draft." Common in professional document workflows.
Sharing Annotated PDFs
Before sharing, decide whether you want annotations to be editable by the recipient. If you save annotations embedded in the PDF, the receiver can see but may be able to delete them. To lock annotations permanently, flatten the PDF before sending — this converts all markup to the page content permanently.