To highlight text in PDF documents, open the file in an editor, pick the highlight tool and drag across the words you want to mark, then download the file so the highlights are saved. PDFNova’s PDF Editor includes a highlighter that works in the browser, free, with no sign-up, and the file stays on your device.
Highlighting is easy to do and easy to overdo. This guide gives you the steps, then shows how to mark a document so the highlights actually help you or your reader later.
How to highlight text in a PDF, step by step
- Open the PDF Editor on your phone, tablet or computer.
- Choose your PDF. If it is password protected, enter the password when asked.
- Scroll to the page you want to mark and zoom in until the text is comfortable to read.
- Select the highlight tool.
- Drag across the word, sentence or figure you want to mark.
- Continue through the document. Switch to sticky notes, shapes or freehand drawing when a highlight alone is not enough.
- Download the edited PDF. Your highlights are saved in the new file.
- Open the download once to confirm the marks appear where you expect.
The original file is not changed, so you keep a clean copy for printing or sharing without marks.
Highlight, underline, box or note: which mark to use
The editor has several marking tools. Each one sends a slightly different signal to the reader.
| Mark | Best for | Example |
|---|---|---|
| Highlight | Key facts and phrases inside running text | A deadline in a contract clause |
| Shape (box or line) | Whole blocks, tables, parts of a picture | A row in a price table |
| Freehand drawing | Quick circles, arrows and ticks | Circling a wrong figure |
| Sticky note | Explaining why something is marked | “Please confirm this amount” |
| Added text | Short visible labels on the page | “See page 4” in the margin |
A highlight says “this matters”. A note says why. Used together, they make feedback clear enough that the other person does not have to call you to ask what you meant.
A simple system that keeps highlights useful
Mark less than you think
If half the page is yellow, nothing stands out. Read a paragraph to the end first, then mark only the phrase that carries the point. A handful of words is usually enough.
Give each kind of mark one meaning
Decide what your marks stand for and stay consistent across the document. For example: highlight for facts to remember, a box for things to check, a sticky note for questions. If you use more than one highlight colour, give each colour one meaning and write the key on the first page.
For studying
Highlight definitions, formulas, dates and names. Leave examples and explanations unmarked. When you revise, you can skim the highlights to test yourself and return to the full text only where you get stuck.
For contracts and agreements
Mark amounts, dates, notice periods, renewal terms and anything you want to ask about before you agree. Once the questions are settled and you have a clean final copy, you can sign it. Our guide on how to sign a PDF online for free explains that step.
For reviewing someone else’s work
Combine a highlight with a short note on each point. Keep comments specific, such as “source needed” or “figure differs from table 2”. Send the marked copy back as a separate file so the author keeps the original.
Highlighting scanned PDFs
A scanned PDF is a photograph of a page. There is no real text in it, only a picture of text, so marking behaves a little differently.
- Draw the highlight over the line as you would on paper. Zoom in so the mark covers the words evenly.
- If the scan is tilted and the highlight does not follow the line, use a box shape or a freehand line under the words instead.
- To make the scan searchable and its text selectable in PDF readers, run it through OCR PDF first and save a searchable PDF. Accuracy depends on scan quality.
Troubleshooting
The highlight covers the text and makes it hard to read
Highlights should be see-through. If a mark looks too heavy, especially on a dark or coloured background, use a box outline around the passage instead, which leaves the text fully visible.
My highlights are missing in another app
Make sure you are opening the downloaded, edited file and not the original. The marks live only in the new copy.
I marked the wrong line
Remove or undo the mark in the editor before you download. If you have already saved, start again from the original file, which is why it is worth keeping.
Highlighting is fiddly on a phone
Zoom in and turn the phone sideways for wider lines. Mark one line at a time for long passages. For a heavy marking session, a tablet or laptop is more comfortable.
The printout does not show the highlights well
On a black and white printer, highlights print as grey bands and can darken the text. For documents you will print without colour, use boxes or underlines.
When a PDF is not the best format for mark-up
Highlights and notes are perfect for reviewing a finished document. If you and a colleague are still rewriting the content together, a word-processor file with tracked changes may suit you better. Our comparison PDF vs Word: when to use each format helps you choose. If you only have the PDF, the PDF to Word tool converts text-based PDFs to an editable .docx, though complex layouts need clean-up.
You can also make marked-up documents more visual. A screenshot, stamp or small diagram placed next to a highlighted passage can explain a point faster than words. See how to add an image or logo to a PDF.
Quick checklist
- Read first, mark second.
- Highlight phrases, not paragraphs.
- Keep one meaning per type of mark.
- Add a note wherever the reason is not obvious.
- Download, reopen and check the file before sharing.
Frequently asked questions
How do I highlight text in a PDF for free?
Open the PDF in a free browser-based editor, select the highlight tool, drag across the text and download the file. No installation or account is needed with PDFNova.
Can I highlight a PDF on my phone?
Yes. The editor works in mobile browsers. Zoom in, drag across the line with your finger and save the file to your phone.
Why can’t I highlight text in my PDF?
The file is probably a scan, so a reader app sees no selectable text. Draw the highlight over the line in an editor, or run OCR to create a searchable copy first.
Do highlights stay when I share the PDF?
Yes, as long as you share the downloaded, edited copy. The marks are part of that file and appear for anyone who opens it.
Good highlighting turns a long document into something you can review in a minute. Open the PDF Editor, mark what matters and download your annotated copy.