Free
Highlight and comment on a PDF
Mark up a document and leave notes that other PDF apps can open.
Free, with no account, no watermark and no page limit.
Updated 25 October 2026
The short answer
PDF Coast lets you highlight, underline and comment on PDFs for free. Open the file, choose Comment at the top of the window, pick a tool and a color, and drag across the text. Add comments from the Comments panel, reply to them and set a review status. Everything is saved as standard PDF annotations, so Adobe Acrobat and other PDF apps show the same comments.
- Price
- Free, no watermark
- Your file
- Stays on your PC, never uploaded
- Internet
- Not needed
- Works on
- Windows 10 and 11
How to do it
- Open the PDF and choose Comment at the top of the window.
- Pick Highlight, Underline or Strikeout, choose a color, and drag across the words.
- Open the Comments panel to add a comment, reply, or mark it Accepted, Rejected or Completed.
- Save. Shapes, arrows, stamps and measurements are saved the same way.
Highlight and comment online, or on your PC?
Online converters are handy on a phone. For anything private, a desktop app is safer.
 PDF Coast |
Typical online converter | |
|---|---|---|
| Your file is uploaded | Never | Yes, to their servers |
| Works without internet | Yes | No |
| Limits on free use | None on free tools | Daily or file-size limits are common |
| Account | Not needed | Often needed after a few files |
Questions
Will Adobe Acrobat show my comments?
Yes. PDF Coast writes highlights, notes and replies as standard PDF annotations, and review statuses are read by Acrobat too. A review can start in one app and finish in the other.
Can I export the comments?
Yes. The Comments panel can export a summary of every comment, and import comments that someone else exported.
Is it free?
Yes. Highlighting, commenting, shapes, stamps and measuring are all free, with no watermark and no account.
Is my file uploaded anywhere?
No. PDF Coast opens and saves the file on your own computer, and works with the internet switched off. Nothing about the document is sent anywhere.
Related tools
-
Pro
Edit PDF text
Click a paragraph and change the wording. The text reflows as you type, and the page keeps its layout.
-
Free
Fill and sign
Type into the fields, tick the boxes and sign. It works on scanned forms too.
-
Free
Merge PDF
Combine as many PDFs as you like, in the order you want. Free.
-
Pro
PDF to Word
An editable .docx with real paragraphs, tables, headers and footers. Converted on your PC.
Get PDF Coast for free
Everyday PDF work is free forever. Pro is US$26.49 once, and you can try every Pro tool free for 14 days. No account, no card, no subscription.
Windows 10 and 11, 64-bit. English, 简体中文 and 繁體中文.