Highlight a PDF in 4 steps
- 1
Open Highlight PDF
Go to Highlight PDF and select the document. The Highlight tool is active.
- 2
Drag across the text
Press at the first word and drag to the last, just as you would select text. On one line, only the characters between your start and end points are marked. Across several lines, the first line runs from your start point to its end, middle lines are covered whole, and the last line stops where you let go.
- 3
Pick a color
The default is yellow at 40% opacity. Change Highlight color for a color-coding system, and raise or lower Opacity to make it stronger or fainter.
- 4
Save PDF
Click Save PDF when you are done. The download ends in -highlighted.pdf.
Highlighting scanned PDFs and images of text
Snapping needs real text in the file. On a scanned page, the tool shows "No selectable text on this page (it may be scanned)" and your drag becomes a plain highlighted rectangle instead. That still works well: drag a box tightly around each line. If you want the highlights to snap, make the scan searchable with an OCR tool first.
Tips for clean highlights
- Two-column pages: highlight one line at a time, or keep multi-line drags inside one column's lines. A drag across several lines extends the first line to the end of the page line, which can spill into the next column.
- Color-code: for example yellow for key points, green for definitions, pink for questions. Each new highlight uses the last color you chose.
- Undo a bad drag with Ctrl+Z (Cmd+Z on Mac), or switch to Select, click the highlight and press Delete.
- Vertical or rotated text is not detected for snapping. Drag a box over it instead.
Does highlighting cover or change the text?
No. The color is blended with a multiply effect, the way a real highlighter pen works, so dark text stays fully readable and the words remain selectable and searchable.
Be aware of how it is saved. The highlight is drawn into the page content rather than stored as a highlight annotation. It shows and prints in every reader, but it will not appear in Acrobat's or Preview's comment list, and nobody can remove it with a click later. If a reviewer needs to reply to your marks, pair the highlights with comments or sticky notes, which are saved as real annotations.
Highlight vs. underline vs. strikethrough
All three snap to text the same way. Highlighting is best for passages you want to find again. Underline PDF is subtler and survives black-and-white printing better. Strikethrough signals that text should be deleted, which is the usual mark when proposing edits to a contract.
Highlight a PDF on Mac or iPhone
In macOS Preview, select text and choose Tools > Annotate > Highlight Text. On iPhone and iPad, open the PDF in the Files app, tap the Markup button and pick the highlighter. Both save highlights as annotations that other apps can edit.
Frequently asked questions
Can I highlight in colors other than yellow?
Yes. Any color from the picker works. Light colors at around 30% to 50% opacity keep the text easiest to read.
Why does my highlight cover more than I selected?
Highlights widen to whole characters, and multi-line drags cover full middle lines. For a precise fragment, highlight one line at a time.
Can I remove a highlight after saving?
Click Edit again on the result screen to change it. Once you leave, the highlight is part of the page. Keep your original file if you might want an unmarked copy.
Will highlights print?
Yes. They are part of the page, so they print in color, or as light gray on a black-and-white printer.