Annotate a PDF

Mark up a PDF with highlights, notes and drawings that open in any reader.

or drop it here · it never leaves your device

Processed in your browser. Your files are never uploaded. Check it yourself

How to annotate a PDF without special software

Reviewing a document usually means marking it up: highlighting the sentence that worries you, circling a figure, adding a note that says “check this with finance”, and passing it back. You don’t need expensive software for that. This tool puts the common markup tools on a large page preview, and saves your marks as standard PDF annotations that any reader can open, edit or delete.

Because the marking happens in your browser, a draft contract or an internal report doesn’t have to be uploaded to be commented on. If you are setting up a review with several people, our guide to annotating a PDF for review covers colour conventions and how to merge feedback.

1
Open the PDF
Press Choose a PDF or drop the file on the panel. The page appears large with a toolbar of eight tools above it: Select, Highlight, Underline, Strike-through, Sticky note, Rectangle, Pen and Text box. Undo and Redo sit in the file bar. Highlight is chosen to begin with, in yellow. Use the page arrows under the preview to move through the document.

Password-protected files ask for the password first and are unlocked in memory. The annotated copy you download has no password, so add one afterwards with Protect PDF if needed.
2
Mark up the page
Pick a tool and a colour, then act on the page:
- Highlight, Underline and Strike-through: drag a rectangle over the line you want to mark. Each drag makes one mark, so a passage of three lines takes three drags.
- Sticky note: click where the note should sit, then type your comment in the panel on the right.
- Rectangle: drag to draw a box outline in the colour and thickness you chose, to ring a figure or a table.
- Pen: draw freehand with a mouse, finger or stylus.
- Text box: drag an area, then type. Choose from four sizes, 10, 12, 16 and 20 points.
Colours are yellow, green, pink, blue, red and black. Line thickness is thin, medium or thick (1.5, 3 and 6 points). On a keyboard, press Place in the middle to drop an item on the page, then use the arrow keys to move it and Shift with the arrows to resize it.
3
Select to adjust anything you added
Switch to Select and click a mark. Drag it to move it, drag its handles to resize it, press a colour to recolour it, change its line thickness or text size, edit the text of a note or text box, or press Delete to remove it. Undo and Redo step back and forward through every change. Annotations that were already in the file are drawn on the page so you can see them, but cannot be selected or moved here.
4
Save and download
The button at the bottom of the options panel counts what will be saved, for example Save 5 annotations. Press it. The result card lists how many highlights, underlines, notes and so on were added and on which pages, and shows a preview of the first annotated page. Download yourfile-annotated.pdf. From the card you can go on to Flatten PDF to lock the marks into the page, protect the file, or compress it.

Annotate PDF features

Highlight, underline and strike-through text
Sticky notes with your comment
Rectangles, freehand pen drawing and text boxes
Six colours, three line thicknesses and four text sizes
Select, move, resize, recolour and delete anything you added
Undo and redo
Saved as real PDF annotations that open in any reader
Keyboard controls for placing and moving items

Annotating a PDF without uploading it

Your file is read into this browser tab. The page previews are drawn on your device, and your annotations are added to a copy of the file on your device. Nothing is uploaded.

The annotations are saved as standard PDF annotation objects: highlight, underline, strike-out, text (sticky note), square, ink and free text. That is what other readers expect, so your marks show up in browsers, desktop readers and phones, and can be edited or deleted there too.

Highlight, underline and strike-through are placed by dragging a rectangle over the text, so size the box to the line you want to mark.
They stay editable. To lock annotations into the page so nobody can change them, run the result through Flatten PDF.
Annotations already in the file are kept and shown on the page, but are not selectable here.
Empty text boxes are skipped when you save.

How to prove your file never left your device: a two-minute Network-tab and offline test you can run on this tool.

Worked example

Reviewing a draft policy

You have a 6-page draft policy to return by the end of the day. Open it, choose Highlight in yellow and drag across the two sentences that need rewording. Choose Sticky note, click next to them and type “Can we say 30 days here?”. Use Strike-through on a paragraph that should go, and Rectangle in red around a table total.

Press Save 5 annotations and download policy-annotated.pdf. Your colleague opens it in their usual reader and sees the highlights and notes, and can reply to them there.

Good to know

Use one colour for each reviewer or each type of comment, so the page can be read at a glance.
Received a revised copy and want to know what changed? Compare PDFs lists every difference and can mark them on a copy.
Keep highlights narrow, one line at a time, so the text underneath stays easy to read.
To type directly on a form, use Edit and fill. Annotations are for comments and markup.
Annotated a file by mistake? Delete a mark by selecting it and pressing Delete, or undo with the Undo button.

What “real PDF annotations” means, and why it matters

A PDF page can carry a list of annotations: small objects laid over the page that are not part of its content. Each has a type (called a subtype), a rectangle saying where it sits, a colour, and often some text. The types this tool writes are Highlight, Underline, StrikeOut, Text (the sticky note), Square (the rectangle), Ink (the pen) and FreeText (the text box).

Three details separate a proper annotation from a picture of one.

Geometry that readers understand. A highlight stores its quadrilateral area. A pen stroke stores the list of points. A note stores its position and its comment. That is why other programs can list them in a comments panel, move them or delete them.
An appearance stream. Each annotation also carries a small drawing, saved with it, that says exactly how it should look. Readers that can draw annotations on their own use their own rendering; readers that cannot, including many viewers on phones and in browsers, simply draw the saved appearance. This is what makes the marks look the same in different places.
Transparency for highlights. A highlight is stored as see-through colour over the text, not as an opaque fill, so the words remain readable.

The tool places marks using positions on the page as you see it, and converts them for you, so pages that are rotated, or whose visible area is smaller than the stored page, are annotated where you clicked.

When annotating is the right job, and when it is not

Typical uses

Reviewing a draft. A policy, a contract or a thesis chapter: highlight the problem sentence, add a note with the suggested change, strike through what should go.
Teaching and study. Colour-code a reading: yellow for definitions, green for examples, red for things to check. Sticky notes take the place of margin scribbles.
Checking a drawing or plan. Ring a dimension with a rectangle, add a text box saying “check this”, and send it back.
Marking up a scan. Pen strokes and text boxes work on any page, scanned or typed.
Sign-off notes. A short text box saying “Approved, 12 March” in a corner, when no formal signature is needed.

Where other tools fit better

Filling in a form or typing into a document. Use Edit and fill. Annotations sit on top of a page; they are comments, not the document’s content.
Signing. Use Sign PDF.
Hiding information. Annotations hide nothing. A black rectangle is just a mark on top. Use Redact PDF.
Making the marks permanent. They stay editable until you flatten them with Flatten PDF.
Marking the actual words. This tool highlights an area of the page, not selected text. It is not linked to the words beneath, so if the text later moves (for example after editing), the highlight does not follow.

How the annotations behave in other readers

Annotations are standard, so they open widely, but readers vary in what they let you do with them.

Where	What to expect
Adobe Acrobat and Reader	Marks appear and are listed in the Comments panel. Notes show their text, and you can reply to or edit them.
Browser viewers (Chrome, Edge, Firefox)	The marks are displayed. Editing support differs by browser and version, so do not assume you can modify them there.
Apple Preview and phone viewers	The marks are displayed and Preview generally lets you work with them. Check on the device that matters if the recipient will rely on it.
Printing	Most readers have a print option for “Document and markups” or “Document only”. If a printed copy is missing the marks, check that setting.
Conversion to Word or images	Converters that rasterise the page include the marks. Converters that work from page text often leave them out. To be sure, flatten first.

When you are sending a marked-up file to several people, test it once in the reader your recipient is likely to use. If the review needs to be robust, the safest route is to ask colleagues for their comments as separate files and combine the results yourself. Our guide to annotating a PDF for review covers colour conventions and how to gather feedback.

Doing it in Acrobat, Preview, Word or Google Docs

Acrobat Reader and Pro have a full comment toolkit with replies, stamps, status marks and shared reviews. The free Reader can add basic comments. If you are running a formal multi-person review, use that. This tool is for one person marking up one copy.
Apple Preview has a Markup toolbar with shapes, text and notes. Its annotations are standard PDF annotations, so they move between devices, but the tool set differs from ours, and colours and styles vary.
Microsoft Word opens a PDF by converting it into a Word document, which rewrites the layout. Comments you add in Word do not go back into the PDF as annotations.
Google Docs and Drive preview a PDF and allow comments on the file inside Drive, but those comments live in Drive, not in the PDF, and do not travel with the file.

The advantage of annotating the file itself is portability: the marks are inside the PDF and go wherever the PDF goes, with no account, no shared workspace and no subscription.

Two worked examples with numbers

The numbers are round figures to show how marks are counted. They are not measurements.

Reviewing a 6-page policy

You read through and decide to mark: four sentences to reword (four highlights, each of one line), two sentences that run onto a second line (two extra highlights), one paragraph to remove (one strike-through), three questions (three sticky notes), and one table total to ring (one rectangle). That is 11 marks, shown on the button as “Save 11 annotations”. The result card lists them by type: 6 highlights, 1 strike-through, 3 sticky notes, 1 rectangle, on four pages.

If a note was created and left empty by mistake, it would be saved as an empty note. Select it and delete it before saving, or it will appear to the reader as a blank pin.

Annotating a scanned plan

You are marking up a single scanned A3 plan. Draw a thick red pen stroke round the area in question (about 6 points wide, so it shows clearly when the page is shrunk to fit a screen), add a 16-point text box saying “Check boundary here”, and a green rectangle round the dimension label. Three marks, one page. Because it is a scan, there is no text to highlight; the pen and rectangle do the work.

Limits and edge cases

Rectangles, not text selection. Highlight, underline and strike-through are placed by dragging over the area. Keep each drag to one line, or the mark will cover the gap between lines.
Existing annotations are kept but not editable here. If the file already has comments from a reader, they remain and are shown on the page. Use that reader to change them.
Empty text boxes are skipped. A text box with no text is left out when you save. The panel says how many were skipped.
The text box uses standard fonts. Very unusual characters may not display in every reader, so keep comments to normal letters and punctuation.
Signed PDFs. The file is rewritten when it is saved, so any digital signature will no longer validate. Annotate before signing.
The author is not recorded as a name you choose. If a reviewer’s identity matters, say so in the note text.
Touch. While a drawing tool is active, the page does not scroll with one finger. Switch to Select, or use the page arrows, to move around.

Privacy: your comments are as private as the document

Notes on a draft are often more sensitive than the draft: “we can’t agree to this”, “ask legal”, “her figures don’t add up”. The preview is drawn in your browser, your marks live in the tab’s memory, and the annotated file is built on your device. Nothing is uploaded, including the text of your notes, and there is no account, shared workspace or cloud copy.

You can verify this with the Network tab in your browser’s developer tools while you add a note and save. The verification guide has a step-by-step version, including doing the whole job with your connection switched off.

Annotate PDF: troubleshooting

I drew a highlight but it does not appear on the page: Check that the tool was active (it is highlighted in the toolbar) and that you dragged rather than clicked. A very small drag can be too small to register. Try again with a longer drag.
“Save” is greyed out: Nothing has been added yet, or the only items are empty text boxes, which are skipped. Add at least one mark or type some text.
The page will not scroll on my phone or tablet: Drawing tools capture touch so you can draw. Switch to Select, or use the page arrows under the preview, to move through the document.
I cannot move or delete a comment that was already in the file: Existing annotations are shown but are not selectable here. Remove them in the reader that made them, or clean them out with Remove metadata.
The highlight covers the text and I cannot read it: Highlights are saved as see-through colour. A dark colour, such as black, will still hide text. Use yellow, green or pink for highlights, and undo the dark one.
My marks are missing when I print: Most readers have a print setting for “Document and markups”. Alternatively, flatten the annotated file with Flatten PDF so the marks become part of the page.
The marks appear in one reader but not in another: Not all readers display every annotation type in the same way. Try Acrobat or a browser viewer to confirm. If the recipient cannot see them, flatten the file.
A text box looks cut off: The box was too small for its text. Select it, drag a handle to enlarge it, or choose a smaller text size.
“This PDF needs a password”: Enter the password at the prompt. Without it the file cannot be opened.

Glossary

Annotation: An object laid over a PDF page, such as a highlight, note or drawing. It is not part of the page content.
Appearance stream: A small saved drawing inside an annotation that tells any reader exactly how to display it.
Subtype: The kind of annotation: Highlight, Underline, StrikeOut, Text, Square, Ink or FreeText for the tools here.
Sticky note: A Text annotation: a small icon on the page that opens to show a comment.
Ink annotation: A freehand stroke stored as a list of points. Created by the Pen tool.
Free text: An annotation that displays typed text directly on the page. Created by the Text box tool.
Flattening: Turning annotations into part of the page, so they can no longer be moved or deleted.
Point: A unit of 1/72 of an inch, used for line widths and text sizes in a PDF.

Annotate PDF: frequently asked questions

Will my annotations open in other PDF readers?

Yes. They are saved as standard PDF annotations, so they appear in browsers, desktop readers and phone apps, where they can also be edited or deleted.

Can I edit or delete annotations after I save?

In this tool you can change everything before you save. Once saved, you can edit or delete them in any reader that supports annotations, or load the file here again and add more.

How is annotating different from Edit and fill?

Annotating adds comments and markup on top of a page without changing it. Edit and fill is for filling in forms and adding text, shapes and images into the document.

How do I make the annotations permanent?

Run the annotated file through Flatten PDF. That bakes them into the page, so they can’t be moved or deleted.

Can I annotate from a phone or tablet?

Yes. Touch works for drawing and placing items, and you can use your finger or a stylus. Drawing tools stop the page scrolling while active, so switch to Select to scroll with one finger.

Is my document uploaded?

No. The page previews, your marks and the saved file all stay in your browser. You can check yourself.

Does the highlight cover the text?

No. Highlights are saved as a see-through colour that sits on top of the text, so the words stay readable.

Can I use the keyboard instead of the mouse?

Yes. Pick a tool, press Place in the middle, then use the arrow keys to move it and Shift with the arrows to resize it. Press Delete to remove the selected item.

How many annotations can I add?

There is no fixed limit in the tool. The button shows the running count. Very large numbers of marks use more memory on your device, so on a phone it is better to work in batches.

Can I highlight several lines at once?

Each highlight is one rectangle, so mark one line at a time, or drag a taller rectangle if the gap between lines can be covered too. Multi-line text takes one drag per line.

Do the annotations show who made them?

This tool does not ask for an author name. If you need the reviewer’s identity to be clear, put their initials in the note text or use a different colour for each reviewer.

Can I annotate a signed PDF?

You can, but the file is rewritten when saved, so the signature will no longer validate on the annotated copy. Keep the signed original and send the annotated version as a separate working copy.

Page updated 25 October 2026 · By the PDFMagpie team