Highlight text in a PDF
Mark passages with a highlighter, keeping the text intact.
Or drop one anywhere on this page
What to know about Highlight PDF
Marking up a document is how most people read a long one: a colour over the clause that matters, so it can be found again in a hurry. This does that by the words rather than by the rectangle — click a passage and the highlight takes the shape the document gave it, on rotated pages as readily as upright ones. The colour sits behind the text, so everything underneath stays selectable and searchable, and the whole job happens on your own device.
How to highlight a PDF
- 1
Open the document
Choose the PDF or drop it here. Its text layout is read on your device, with nothing sent anywhere.
- 2
Click the passages
Each block of text on the page becomes a target. Click the ones you want marked, or tab through them in reading order.
- 3
Save the marked copy
Download the PDF with the highlights drawn behind the words.
What Highlight PDF accepts and produces
- Input
- One PDF with selectable text to mark, plus the passages you pick.
- Output
- The same document with the passages you chose marked, and the text underneath still selectable and searchable.
- Limits
- There is nothing to highlight on a scanned page until it has been through OCR, because the tool marks real text rather than drawing a box where you dragged.
- Offline
- Yes, once the rendering engine has been fetched on your first visit.
Why Highlight PDF here
- Highlights follow the text, not a rectangle you have to draw
- The words underneath stay selectable and searchable
- Every passage is a keyboard target, in reading order
- Works on rotated pages and across embedded and subset fonts
Where your file goes
Nowhere. This tool runs inside your browser, and the page is served with a policy that forbids it from sending your document anywhere. You can confirm that yourself: open your browser’s developer tools, watch the Network tab, and process a file.
Questions
Does highlighting hide or remove anything?
No, and the distinction matters. A highlight is a translucent colour drawn behind the words: the text stays exactly where it was, still selectable, still searchable, still copyable. If your aim is to make something unreadable or unrecoverable, highlighting is the wrong tool and Redact PDF is the right one — it rebuilds the page and destroys what was underneath.
How do I choose what gets highlighted?
Click the passage on the page. The document already describes where each block of text sits, so the highlight takes that shape rather than whatever rectangle you manage to drag. You can also tab through the passages from the keyboard, in the order they read.
Why can I not highlight a line or a table border?
Because those are drawings, not text. This tool highlights what the document stores as text, which is why the colour follows the words and stops at the end of them. Rules, borders and other vector graphics are left alone deliberately.
Does it work on a scanned document?
Only if the scan has a text layer. A plain scan is a picture of a page with nothing to select, so there are no passages to click and the tool will tell you it found none rather than inviting you to highlight nothing.
Can I highlight across several pages?
Yes. Move between pages and choose passages on each; the selections are kept as you go and applied together when you save.
Will the highlight show in every PDF viewer?
Yes. It is drawn into the page content with a multiply blend, which is how a marker behaves on paper — the colour darkens what is under it rather than covering it — so it appears in any reader and prints as you see it.
Can I remove a highlight afterwards?
Not from within this tool. The colour becomes part of the page, so keep your unmarked copy if you might want it back. Selections can be cleared freely before you save.
Does highlighting change the rest of the document?
No. The rectangle is appended to the page, so text, images, links, bookmarks, form fields and attachments are all untouched. Nothing is rasterised or flattened.
Is my document uploaded to highlight it?
No. Reading the text layout and drawing the highlights both happen inside your browser. You can watch the network panel while you work, or switch the network off entirely — it still works.