Underline text in a PDF
Click a line to underline it, in any color. Undo or delete any mark later.
How do I underline text in a PDF for free?
Open PDFkitt's Underline PDF tool (pdfkitt.com/underline-pdf/): open the PDF, pick a color, click lines of text, then download. It is free, needs no account and adds no watermark, and it runs entirely in your browser — the file is never uploaded to a server.
- Price
- Free — no trial, no paid tier, no watermark
- Account
- Not needed
- File upload
- None — processed on your device, in the browser
- Limits
- No daily quota and no file-count limit
- Works on
- Windows, macOS, Linux, iPhone, iPad and Android, in any modern browser
Updated · by the PDFkitt team
Underlining is the classic way to mark a definition, a key clause or a sentence to come back to. Choose Underline text, pick a color and click any line; a neat underline is placed along its baseline. Every mark can be selected and deleted, and undo reverses the last one.
Underlines are exported into the page content so they show up everywhere. Combine them with highlights, strike-throughs and sticky notes for a full review — all in the same session, all in your browser.
How to underline text in a PDF
- Open the PDF The Underline tool is pre-selected.
- Pick a color Any swatch or a custom color.
- Click lines of text Each click underlines one line.
- Download Marks are saved into the PDF.
Why use PDFkitt to underline PDF?
The file is processed inside your browser tab. Disconnect from the internet after the page loads and it still works.
No signup, no email, no daily quota, no page limit, no watermark. Use it as often as you like.
Phone, tablet or desktop, in Chrome, Safari, Edge and Firefox. Nothing to install.
Frequently asked questions
Can I underline text in a scanned PDF?
Draw a straight line with the Line tool in the Draw menu instead.
Can I change the thickness?
The underline thickness follows the text size automatically.
Is the document uploaded?
No, the whole editor runs in your browser.