How to highlight and annotate a PDF on Android

To annotate a PDF on Android, open it in an app with markup tools, select the text you want to mark, then choose highlight, underline or strike-through. You can also drop sticky notes on a spot or draw freehand with your finger. Save the file and the marks travel with it, so anyone who opens it sees them.

What does it mean to annotate a PDF?

To annotate a PDF is to add marks and comments on top of the page without changing the original text. The PDF format has a standard set of annotation types, which is why marks made in one app usually show up in another.

The common types are:

• Highlight: a coloured band behind a line of text, like a highlighter pen.
• Underline: a line under the text, often used for key terms.
• Strike-through: a line through text, usually to suggest deleting it.
• Sticky note: a small icon that opens a comment when tapped.
• Freehand drawing: circles, arrows or handwriting made with your finger or a stylus.

How to annotate a PDF on Android, step by step

1. Open the PDF in an app with annotation tools.
2. Choose the highlight tool, then drag your finger across the text you want to mark. On a digital PDF, the highlight snaps to the line of text.
3. Switch to underline or strike-through for other kinds of mark.
4. To leave a comment, choose the note tool, tap the spot on the page and type your note.
5. To circle something or add an arrow, use the drawing or pen tool.
6. Zoom in for precision when marking small text.
7. Save. If you want to keep a clean copy, save the annotated version under a new name.

Why won't my highlight snap to the text?

If the highlighter draws a rough rectangle instead of following the words, the PDF is probably a scan. A scanned page is an image, so the app cannot see where the lines of text are. You can still draw over it, or run OCR to add a text layer. See how to make a scanned PDF searchable with OCR.

Using colours with a purpose

Colour is only helpful if it means something. A simple system works well when studying or reviewing:

• Yellow for key points.
• Green for definitions or terms to learn.
• Pink or red for things you disagree with or need to check.
• Blue for quotes you might reuse.

Pick a system before you start and stick to it, so a quick glance at a page tells you what kind of note each mark is.

Annotating for review versus annotating for yourself

Reviewing someone else's document. Use strike-through for suggested deletions and sticky notes for suggested wording. Keep notes short and specific: "Change to 30 days?" is easier to act on than "This seems off". Send the annotated copy back and keep the original.

Studying or reading for yourself. Here the marks are just for you. Highlight less than you think you need. If everything is yellow, nothing stands out.

If your notes are private and you do not want them inside a file you will share, keep them separately from the document's annotations, or work on a personal copy.

Can annotations be removed or changed later?

Yes. Annotations sit on top of the page, so most apps let you tap one to edit or delete it. That flexibility is useful, but it also means a reviewer's comments can be removed by anyone. If you want the marks fixed into the page, flatten the file. Our explainer on what flattening a PDF means covers when that is a good idea.

Annotations are not redaction

Drawing a thick black line over a name looks like it hides it. It does not. The text underneath is still in the file and can often be selected, copied or revealed by deleting the drawing. To remove information for real, use a redaction tool. Read how to redact a PDF properly.

Annotating PDFs with PDF Burrow

PDF Burrow has a Highlight & Annotate tool for highlighting, underlining, strike-through, sticky notes and drawing. There is also a separate Sticky Notes tool for private notes on any page that reappear when you reopen the PDF. Both work on your phone without uploading the file.

Frequently asked questions

Will my highlights show up on a computer?

In most cases, yes. Standard PDF annotations are understood by most desktop readers. Very old or simple viewers may not show every type, such as freehand drawings.

Can I annotate a password-protected PDF?

You need to open it with the password first. Some protected files also block editing, in which case the owner needs to remove that restriction or send you an unrestricted copy.

Do annotations print?

Highlights, underlines and drawings usually print. Sticky note text often does not, because only the small icon sits on the page. Flatten the file or check print settings if you need comments on paper.

How do I highlight with a stylus?

Choose the highlight or pen tool and use the stylus as you would a finger. Many phones also support palm rejection, which stops your hand from leaving stray marks.