How to underline or strike through text in a PDF on Mac
Two marks that say different things from a highlight: this matters, and this should go.
Highlight, underline and strikethrough are the three classic marks, and in a review they mean three different things. Using them as though they were interchangeable throws away most of their value.
Underline and strikethrough is part of Premium, so it carries a small lock in the document actions panel and in the menu bar. The lock is a label rather than a barrier — you can open the feature and see what it does before deciding to unlock it. Reading and every page operation stay free.
What each one says
| Mark | What a reader understands |
|---|---|
| Highlight | Look here. Something on this line matters. |
| Underline | This specific phrase matters — and the words stay perfectly legible under the line. |
| Strikethrough | This should be removed. |
Underline is the right choice when a highlight would be too loud, or when the text is already on a coloured background, or when the document is going to be printed in black and white and a pale highlight would vanish.
Marking text, step by step
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Choose the tool
Underline and strikethrough sit alongside the highlighter in the tool pill along the bottom of the window.
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Pick a colour
Both take any colour. Red strikethrough is the convention for deletion, and conventions are worth following when someone else has to read the result.
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Select the text
Drag across the words. The mark follows the shape of the line, including across a line break.
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Add a note if the mark needs a reason
A struck-through paragraph with no explanation is an instruction. A struck-through paragraph with a note saying why is an argument. The second one gets accepted more often.
Striking through versus actually deleting
A strikethrough is a suggestion: the words are still there, marked. Editing the text removes them. Which you want depends on who the document is for.
If you are reviewing someone else's document, strike through — they need to see what you propose to cut, not discover it missing. If you are fixing your own document before sending it, edit the text properly and let the reader see the finished version.
All three of these need selectable text. On a scan, run Make Searchable first, or use the pen and shapes tools, which work on any page at all.
Reviewing your own pass
The annotations list in the sidebar collects every mark in the document in one place, so before you send a marked-up document back you can step through your own underlines and deletions and check they still say what you meant. It is a much better final check than scrolling.
Frequently asked questions
How do I underline text in a PDF on a Mac?
Choose the underline tool from the pill along the bottom of the window, pick a colour and drag across the words.
How do I cross out text in a PDF?
Use the strikethrough tool the same way. Red is the usual convention for a proposed deletion.
Does a strikethrough delete the text?
No. It marks the words as proposed for removal; they are still in the document. Editing the text is what actually removes it.
Why can I not underline my PDF?
The page has no selectable text — it is a scan. Run Make Searchable over it first, or use the pen and shapes tools, which work on any page.
Will these marks print?
Yes. They are stored in the document and print with it.