To highlight a PDF online without covering the text, upload a working copy, drag a narrow highlight over the passage, save the result as a new version, then reopen the downloaded PDF and check every mark. Use notes or outlined rectangles for review instructions. If the page is a scan, the highlight can still mark the visible area, but it will not make the words searchable.
Quick workflow
- Keep the original and upload a working copy to the PDF Highlighter.
- Drag tightly across the words; avoid covering lines above or below.
- Add a text note or rectangle when the reason for the mark is not obvious.
- Save a version and download the marked copy.
- Reopen that download and verify the text, pages, marks, and filename.
A highlight is not redaction. It draws attention to content; it does not remove the underlying information. Do not use a colored rectangle to hide a name, account number, or other sensitive text.
Choose the Right Kind of Mark
| Your document and goal | Best action | Important limit |
|---|---|---|
| Selectable text; mark a passage | Draw a tight visual highlight | Check that the overlay does not obscure letters |
| Scanned page; mark a visible line | Highlight the visible area | The scan remains an image; run OCR separately if you need search or copy |
| Ask a reviewer to change something | Add a note or outlined rectangle | A mark is clearer than silently changing source text |
| Hide confidential information | Use a true redaction workflow | Highlighting does not delete text or image data |
| Signed PDF; add review marks | Preserve the signed original and mark a copy | Saving changes creates a different file and can affect signature validity |
How to Highlight a PDF With PDFCheck
1. Start with a copy
Duplicate the PDF before marking it, especially when it is signed, submitted, archival, or your only copy. Give the working file a useful name such as proposal-review-2026-07-21.pdf. This keeps the untouched source easy to identify.
2. Upload it to the highlighter
Open the PDF Highlighter and choose the working copy. PDFCheck opens the editor in highlight mode. For confidential or regulated documents, confirm that an online upload is allowed by your organization before proceeding.
3. Draw narrowly across each passage
Drag over only the words you need. The tool uses a translucent yellow visual overlay so the page remains readable. If the block touches a neighboring line, undo it and draw again rather than accepting an ambiguous mark.
4. Add context when color is not enough
Use a text note for an instruction such as “confirm this date” or an outlined rectangle around a diagram or table. If you need to change the actual wording, make a separate copy in the PDF Editor and review the edit independently.
5. Save, download, and reopen
Save a version before downloading so you can return to the work in the same browser session. Download the result, close the editor preview, and open the downloaded file in the viewer your recipient uses. Check page count, text legibility, mark placement, notes, and filename. Send that exact tested copy.
Can You Highlight a Scanned PDF?
Yes, you can place a visual highlight over a scanned page because the mark targets an area of the page. But the visible words are still pixels. PDFCheck’s highlighter does not run OCR, create selectable text, or add a searchable text layer.
If you need to search, quote, or copy the words, first follow the scanned-PDF search and OCR workflow. Keep the scan as evidence and review OCR output against the page image; recognition can misread names, dates, totals, and unusual layouts.
Troubleshooting Highlights
| Problem | Likely reason | What to do |
|---|---|---|
| You cannot select individual words | The page is probably a scan | Use a visual area highlight, or OCR a separate copy when you need searchable text |
| Yellow covers too much text | The overlay is too tall or wide | Undo it and redraw tightly around the intended line |
| A mark seems missing after download | The wrong copy is open or the viewer has stale state | Check the filename and reopen the newly downloaded file |
| A signature warning appears | The saved file differs from the signed version | Return to the untouched original and inspect it with the PDF Signature Checker |
| You need information to be permanently hidden | Highlighting is the wrong operation | Use an approved redaction tool, then verify the hidden data cannot be recovered |
Why Highlights and Edits Need Separate Review
The PDF Association glossary describes an annotation as content added to a PDF page, including highlights and comments. PDF tools can represent marks in different ways. PDFCheck writes its visual highlight into a newly saved PDF page, so the result should be treated as a modified copy rather than an untouched original.
Adobe’s current markup guidance distinguishes highlighting and other review marks from editing document content. That distinction matters in approvals: a reviewer can mark a problem without silently replacing the author’s wording.
For signed documents, Adobe’s signed-version comparison guidance explains how to compare a signed version with the current version. Preserve the original, mark a review copy, and repeat the approved signing process only after changes are final.
PDFCheck capability boundary
The highlighter creates translucent visual overlays plus optional text and rectangle marks in a new PDF. It does not run OCR, perform redaction, certify accessibility, or cryptographically validate a signature. Use the dedicated workflow for each of those jobs.
Final Highlighting Checklist
- □ I kept the untouched original.
- □ I used a highlight for emphasis—not to hide information.
- □ I added a note where the reason for the mark was unclear.
- □ I treated scanned text as an image and used OCR separately when needed.
- □ I preserved any signed original and checked the signature before editing.
- □ I reopened the downloaded copy and checked every page and mark.
- □ I am sending the exact file I verified.
Before sending a marked document to someone else, finish with the seven-step PDF preflight checklist. It covers visual review, links, privacy, signatures, recipient requirements, and final-file control.