Can I change the colour after highlighting?

Yes, but only before you download. While you are still editing, highlights are live annotation objects and you can change their colour freely. Once you download the PDF, all highlights are flattened into the page and can no longer be edited.

Will highlights survive printing?

Yes. Flattened highlights are part of the page content, so the printer renders them exactly like the rest of the page.

Do highlights get permanently saved into the PDF?

Yes. When you download the highlighted PDF, all highlights are flattened directly into the page content. They are visible in any PDF viewer without any special software, but are no longer separate, editable annotation objects.

Is it really free to highlight PDFs?

Yes, completely free with no daily limits and no watermarks on the output. No subscription required.

What is the file size limit?

Each PDF can be up to 50MB on the free tier.

Highlight PDF Online Free

Mark important text in any PDF using multiple highlight colors. Color-code sections, mark key passages, and share a highlighted PDF that looks the same in any viewer. No software needed, no account required.

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Up to 50 MB

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Files auto-delete

Free to get started

How to Highlight PDF

1
Upload your PDF
Click the upload area or drag and drop your PDF. Any PDF version is supported.
2
Choose a color and highlight text
Select a highlight color from the toolbar and drag to select the text you want to mark. Switch colors at any time to organize sections by category or importance.
3
Download your highlighted PDF
Download the PDF with all highlights permanently flattened, visible in any PDF reader without plugins.

Why use PDFHaul
to highlight PDFs?

Multiple highlight colors

Yellow, green, blue, pink, and orange. Switch between colors freely. Color-code sections by topic, reviewer, or importance across an entire document.

Highlights flattened permanently

Highlights are baked into the PDF on download, visible in Adobe Reader, Preview, and any browser-based PDF viewer without special software or PDFHaul.

Works across all pages

Highlight text on any page in the document without limitations. Navigate between pages and keep adding highlights until you have marked everything you need.

Files deleted in 2 hours

Your documents are automatically purged from our servers within 2 hours. Not stored, not analysed, not sold.

Who highlights
PDFs?

Highlighting is one of the most universal document tasks: used for studying, reviewing, compliance, and collaborative work.

Students and researchers

Mark key passages in journal articles, textbooks, and lecture notes. Use different colors to separate definitions, evidence, and arguments. Study from a pre-highlighted document rather than re-reading everything from scratch.

Contract and legal review

Highlight key obligations, payment terms, termination clauses, and liability caps in a contract before a meeting or negotiation. Share a pre-highlighted draft to draw attention to the sections that need discussion.

Compliance and audit

Mark the relevant clauses and sections of a regulatory document or policy framework during a compliance review. Color-code by risk level, status, or responsible team for easy reference during an audit.

Document review and editing

Highlight sections that need rewriting, sections that are approved, and sections that need a second opinion. A color-coded markup is faster to discuss than a list of page references in an email.

How PDF highlighting works

Highlighting in a PDF works differently depending on whether the PDF has a text layer. A text-layer PDF (one created digitally, not scanned) contains the actual characters as searchable, selectable data. Highlighting in this case places a semi-transparent colour annotation precisely over the character bounds stored in the text layer.

A scanned PDF is a photograph of a page. It has no text layer unless OCR has been run on it. Without a text layer, there is no character position data to anchor a highlight to. Attempting to highlight text in a scanned PDF produces a rectangle drawn over wherever you clicked, not a highlight that follows word boundaries.

PDFHaul highlights text-layer PDFs only. If your PDF was scanned, you need to run OCR first to create a text layer before highlighting will work correctly. To check: open the PDF and try to select text with your cursor. If you can highlight individual words, the file has a text layer. If selecting highlights the entire page as a single block, it is a scanned image.

Highlight colours available: yellow, green, blue, pink, orange. Highlights are flattened directly into the page content when you download the PDF, they are not stored as separate, interactive PDF annotation objects.

One practical use of colour-coded highlighting: yellow for key findings, green for supporting evidence, pink for items to follow up, blue for definitions. This is common in academic and legal review workflows.

Frequently asked questions

Everything you need to know about highlighting PDFs online

The PDF does not have a text layer. It is either scanned or was created in a way that rasterised the text into images. To check: open the PDF and try to select text with your cursor. If selecting highlights the entire page as a single block, it is a scanned image and needs OCR before text-selection-based highlighting will work.