How to annotate and highlight a PDF on a Mac

With PDF Unlimited (free)

1. Switch to Annotate mode

   Open the PDF in PDF Unlimited and click Annotate in the toolbar mode switcher.

2. Highlight text

   Select a passage and choose highlight, underline or strikethrough. Pick the color in the inspector on the right.

3. Draw and point

   Use the pen for freehand marks, or shapes for rectangles, ellipses, lines and arrows. Set stroke and color in the inspector.

4. Leave comments

   Add a sticky note for a comment that stays tucked away, or a text box when the words should be on the page.

5. Review your marks

   Use thumbnails in the left sidebar to jump between pages. ⌘Z undoes the last mark.

With Preview, built into macOS

1. Show the Markup toolbar

   Open the PDF in Preview and click the Show Markup Toolbar button.

2. Highlight

   Choose Highlight Selection and select the text you want to highlight.

3. Add shapes and notes

   Click Shapes for boxes, lines and arrows, Note for comments, and Text for text boxes. Use Border Color and Fill Color to style them.

A simple color system

Highlighting everything is the same as highlighting nothing. Pick a small system and stick to it. One example:

• Yellow for key points.
• Green for definitions and figures you will quote.
• Pink or red for things to question or check.
• Strikethrough for text you are proposing to cut.
• Sticky notes for your own thoughts, so the page stays readable.

Reviewing someone else's document

For contract or draft reviews, strikethrough plus a sticky note explaining the change is clearer than a scribble. Arrows and rectangles are good for pointing at layout problems in designs. When you send it back, the other person sees your annotations in Preview, Acrobat or most other PDF apps, because they are saved as standard PDF annotations.

For students and researchers

If you read a lot of papers, PDF Unlimited covers highlighting, notes and search well. If you want to export all your notes as text, or you work with LaTeX, look at Skim, a free, open-source reader built for annotating papers. We include it in our roundup of free PDF apps, because it is very good at that job.

Annotations are not redactions

A black rectangle or a thick black highlight hides text on screen but leaves it in the file. If you need to hide information, use true redaction. And if your PDF is a scan and highlights will not stick to the words, run OCR first so the text can be selected.

Keep a clean copy

Annotations are saved into the PDF. If you will need the untouched document later, like a contract you might send to someone else, duplicate it in the Finder before you start marking it up. For study notes, a dated copy per reading session makes it easy to see how your thinking changed.

Need a version where nobody can move or delete the marks? Choose File > Print and Save as PDF to flatten them into the page.

Questions