How to annotate a PDF — marking up, commenting on and signing pages with the PDF Pro annotate tool.
A PDF is meant to be read, but most of the time you also need to react to it — flag a clause, ask a question, circle a number, sign on the dotted line. Annotating is how you write your thinking back onto the page without rebuilding the document. This guide walks the whole job in five steps, run entirely in your browser tab, and covers all six annotation tools one by one.
What you'll need
- A modern browser (Chrome, Edge, Firefox, or Safari from the last two years)
- The PDF you want to annotate, on your device — no account, no signup
- A clear idea of what each page needs: a highlight, a note, a comment, a drawing, or a signature
- A signature ready to go if you plan to sign — drawn with the mouse, typed, or an image to upload
The five steps
Open the annotate tool
Head to the PDF Pro annotate tool. The page loads with the full annotation toolbar ready to use — no signup, no email-confirm wall, no daily page counter, and no upload endpoint to send your document to. Everything you do from here happens inside this one tab.
Open your PDF
Drag the file onto the drop zone or click to browse. The tool reads it straight from your disk and renders the document page by page, just as a reader would show it. Scroll to the page you want to mark up — annotation always happens on the page you can see, so there is no separate "edit mode" to switch into.
Tour the annotation toolbar
The toolbar carries six tools, and each one makes a different kind of mark. Pick a tool, work on the page, then pick another — you can mix all six on the same document. Here is what each one does:
In short: Highlight is for emphasis on existing text, Sticky note and Comment are for adding your own words, Draw is for freehand marks where a highlight won't do, Erase is the undo for anything you placed, and Signature is the dedicated path for signing. You will likely use two or three of them on any given document.
Place, move and edit annotations
Now do the work. Drag the Highlight tool across a sentence to color it; click with the Sticky note or Comment tool to drop a marker and type into it; hold and drag with the Draw pen to circle a figure or sketch an arrow. Nothing is final — annotations you placed can be dragged to a new position, and a highlight or pen stroke can be recolored or re-thicknessed before you move on. If a mark is wrong, switch to the Erase tool and click it away; Erase only removes annotations you added, never the underlying document.
Save the annotated PDF
When the page looks right, download the file. Every annotation — highlights, sticky notes, comments, pen strokes and your signature — is written into the downloaded PDF itself, not stored in a separate layer only PDF Pro can read. That means anyone who opens the file in any PDF reader sees exactly what you marked. Nothing is locked behind a signup or an upgrade; the annotated document is yours the moment it saves.
Download annotated PDFCommon mistakes & gotchas
- Trying to highlight a scanned page. The Highlight tool needs a real text layer to grab onto. On an image-only scan there is no text to select — run OCR first, then highlight.
- Expecting Erase to fix the document. Erase only removes annotations you added. It will not delete original text, images, or anything that was in the PDF before you opened it.
- Confusing a sticky note with a comment. They look similar but behave differently — a sticky note is a tidy collapsible marker, a comment is a threaded remark pinned to a point. Pick the one that matches how the note will be read.
- Forgetting to download. Annotations live in the tab until you save. Close or refresh before downloading and the marks are gone — there is no server-side copy, by design.
- Drawing a signature when a real one is needed. The Signature tool places a visible signature image. If a document needs a cryptographic digital signature, use the dedicated sign tool instead.
Troubleshooting
The Highlight tool won't select any text. Why?
Highlight works by grabbing a real text layer, so it has nothing to catch on a scanned, image-only page. Run the page through OCR first to add selectable text, then reopen it in the annotate tool and the highlighter will work normally.
Will my annotations show up in other PDF readers?
Yes. When you save, every mark is written into the PDF file itself rather than kept in a private layer. Open the downloaded file in Acrobat, Preview, a browser, or any other reader and the highlights, notes, comments, drawings and signature all appear.
Does my file get uploaded to a server?
No. The whole annotation suite runs inside your browser, so the document is read straight from your device and never leaves it. If you want to confirm it, open DevTools, switch to the Network tab, and annotate — you'll see zero file uploads.
I made a mistake — can I remove an annotation?
Yes. Switch to the Erase tool and click the mark you want gone. Erase removes any annotation you added — a highlight, note, comment, drawing or signature — but never touches the original document underneath.
How do I add my signature to the PDF?
Pick the Signature tool. You can draw the signature with your mouse or trackpad, type it and have it styled, or upload an image of a signature you already have. Once created, place it on the page and drag it to sit exactly on the signature line before you save.
Ready to mark up a PDF?
Open the browser annotate tool and run your PDF through the five steps above.