Highlighting text in a PDF is one of the most basic annotation tasks — and one of the most widely supported. Most PDF viewers include highlighting tools, and the process is nearly identical across applications. The main differences are in how you access the tool, the color options available, and what happens to the highlights when the file is saved and shared.
The Basic Method — Works in Most PDF Viewers
In Adobe Reader, Acrobat, Chrome's PDF viewer, and most PDF applications, highlighting works the same way:
- Select the text you want to highlight by clicking and dragging across it
- Right-click the selected text — a context menu appears with a Highlight option
- Click Highlight — the selected text gets a colored background, typically yellow by default
Alternatively, in Adobe Reader you can activate the Highlight tool first (it's in the toolbar or under Tools > Comment), then click and drag to highlight — which is faster when you're marking up multiple sections. With the tool active, every selection is highlighted automatically without needing to right-click each time.
Highlighting in Common Applications
- Adobe Reader (free): Tools > Comment > Highlight Text, or right-click selected text. Multiple colors available. Highlights saved as annotations that display in any PDF viewer.
- Chrome browser: select text and right-click. Chrome's built-in viewer supports basic highlighting. Highlights are saved if you download the annotated PDF afterward.
- Apple Preview (Mac): select text, then Tools > Highlight Text, or use the markup toolbar. Preview supports yellow, green, blue, and pink highlights.
- iPhone/iPad: open the PDF in Files or Books, select text with a long press, choose Highlight from the popup menu. Works well on touchscreens with finger selection.
Using Multiple Colors as a System
Most PDF Annotation tools offer at least four or five highlight colors. Using them randomly wastes their potential — using them consistently creates a review system that's faster to read than notes alone.
A simple color system that works for document review:
- Yellow: important — needs attention or follow-up
- Green: approved or agreed — no action needed
- Pink/Red: must change or problem area
- Blue: reference — useful context but not requiring action
Define the system at the start of any collaborative review and share it with other reviewers. A document where everyone uses colors consistently is far faster to process than one where highlighting is random.
Highlighting Scanned PDFs
Standard highlighting requires selectable text — it doesn't work on scanned image-only PDFs where there's no text to select. If you try to highlight in a scanned PDF, nothing selects, or the entire page selects as one block.
Two options for scanned documents: run OCR first to add a text layer, which then makes the text selectable and highlightable. Or use a freehand drawing tool to draw a highlight shape over the area manually — this is less precise but works on any content. WukongPDF's OCR tool at www.wukongpdf.com adds the text layer that enables standard highlighting afterward.
Are Your Highlights Visible When You Share the PDF?
Yes — highlights saved in a PDF are visible to anyone who opens the file in any standard PDF viewer. They're stored as annotation objects that all viewers display. If you want to share the PDF without the highlights, either remove them before sharing (in Acrobat: Comment > Manage Comments > select all > Delete) or print the PDF to a new PDF to flatten the annotations into the page without the interactive highlight layer. Keep an annotated copy for your records and share the clean version.