Highlight text in any PDF — search and mark up automatically
Type the words or phrases you want to highlight, choose a color, and we'll find every match across your PDF and mark it for you. Faster than highlighting by hand in Acrobat.
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Manually highlighting every mention of a key term across a long PDF is a chore — review a lease for 'tenant' clauses, mark every reference to a defendant in a deposition, flag every 'shall' in a contract. PDFOnly's Highlight PDF tool automates it: type the words or phrases you want to highlight, pick a color, and we find every occurrence across the entire document and mark it for you. Case-insensitive matching, multi-word phrase support, and the highlights are real overlays on the document — not just text replacements.
How to highlight pdf step by step
- 1
Upload your PDF
Files up to 100 MB on the free tier (200 MB on Pro). The PDF needs real text — for scanned PDFs, run OCR first.
- 2
Type your search terms
Comma-separated. Example: 'tenant, landlord, breach' will highlight every occurrence of any of those three words. Multi-word phrases work too — 'force majeure, hold harmless'.
- 3
Choose a color and process
Yellow is the default (most familiar), but pink, green, and blue are also available — useful when you want to use multiple highlight passes for different categories.
- 4
Download the highlighted PDF
The output is a regular PDF with semi-transparent colored overlays placed exactly behind every match. Opens in any PDF reader, looks the same everywhere.
Why highlight pdf on PDFOnly
True text-position highlighting, not approximations
We use poppler's bounding-box extraction to find the exact pixel position of every word match. The highlight overlay sits precisely behind the text — not floating in the margin, not approximated by line.
Multi-term, multi-color in one pass
Search for 'plaintiff' and 'defendant' together, highlight in different colors next time. Faster than hand-highlighting in Acrobat — much faster on long documents.
Output is real PDF, not an image
The text underneath the highlight is still searchable, copyable, and accessible. The highlight is a fill rectangle, not a raster overlay.
What people use highlight pdf for
A few common scenarios. If your workflow looks like one of these, this tool is a good fit.
Mark every mention of a party or term in a legal document
Reviewing a contract or deposition? Highlight every occurrence of the parties' names, key terms ('shall', 'breach', 'liability'), or specific clauses to read selectively.
Highlight key concepts in research papers and textbooks
Studying for an exam or doing a literature review? Type the terms you care about — methodology names, key authors, specific concepts — and let the tool mark every appearance for fast skimming.
Flag risk words in compliance reviews
Compliance officers reviewing audits or vendor docs can highlight words like 'risk', 'breach', 'incident', 'fine', 'violation' across hundreds of pages in seconds.
Mark proper nouns in transcripts
Highlight every speaker name, location, or company in interview transcripts or news archives for thematic analysis.
What you get
- Search-and-highlight every match in one pass — no manual hunting
- Multiple search terms at once (comma-separated)
- Customize the highlight color (yellow, green, pink, blue)
- Case-insensitive matching by default
- Free, no signup, files auto-deleted in 1 hour
- Output is a real PDF with semi-transparent highlight overlays
Frequently asked questions
Does it find text in scanned PDFs?
No — scanned PDFs have no extractable text positions. Run OCR PDF first to make the scan text-searchable, then highlight. After OCR, the position of every recognized word is known, and the tool can highlight as expected.
Are matches case-sensitive?
No — matching is case-insensitive by default. 'Tenant' will match 'TENANT', 'tenant', and 'Tenant'. We may add a case-sensitive option in the future if there's demand.
Will partial-word matches be highlighted?
Yes — we highlight any word that contains your search term. So 'sub' would match 'subscription', 'submit', 'substitute'. If you want exact matches only, surround your term with spaces ('sub ' to limit).
What about regex or fuzzy matching?
Not in v1 — we do simple substring matching. If demand is there, we may add regex/word-boundary options.
Are real PDF annotations created (so I can edit them later)?
Currently we draw filled rectangles, not PDF annotation objects. They look identical to highlight annotations in any reader, but you can't 'edit' them via the annotation tool. If real annotations are important to you (e.g. for review workflows), let us know — we'll prioritize that path.
What happens to the underlying text?
Nothing — the text remains intact and selectable. The highlight is a translucent rectangle drawn behind/over it.
Can I undo the highlights?
Use Flatten PDF then Edit PDF to remove specific overlays, or just re-process from your original. Keep your originals!
Ready to highlight pdf?
Free to use for the basics. Files are auto-deleted within an hour and never used to train AI.
Open Highlight PDF