Adding annotations to a PDF on a Mac PC or Laptop is extremely straightforward! The Mac OS comes built-in with the Preview app, which has far stronger capabilities than the name might suggest. On the Preview app, you can view images and PDFs. On top of that, you can also edit, redact, split and add annotations to your documents!
How To Annotate
Step 1: Open your document
The first thing you need to do is to open your document in Preview. There are two ways to do this, you can right-click on your document and Open With > Preview. Alternatively, you can open the Preview app first and then select your file of choice from the file selector that pops up on your screen.
Step 2: Select the annotation tool
Preview gives you the option to markup and edit your document. The two icons live side by side on the navigation bar within the Preview app, as illustrated below. Selecting the annotation (or highlighter tool) will allow you to highlight, underline or strikethrough the text on your PDF.
To highlight: Select one of the colors from the dropdown list. The highlighter tool will be activated, and you will be able to highlight within the PDF by dragging the cursor across your text.
To underline: Select the underline option from the dropdown list, then drag your cursor across that text you want to underline.
To strikethrough: Select the strikethrough option from the dropdown list, then drag your cursor across the text to strikethrough.
More Editing & Mark Up Options
You can also add shapes and text to your PDF by selecting the markup button instead of the highlight button. This will open up an edit toolbar with additional formatting and annotation options such as adding notes, text, shapes, and lines.
Difference between Draw and Sketch
The Draw and Sketch icons in the markup toolbar look similar but behave differently. Selecting the Draw tool allows you to freehand draw on top of your PDF. However, lines drawn with the sketch tool are smoothened and straightened to perfect curves and straight lines.
Adding Text & Notes
You can also add text and notes to your PDF using the Preview app. To add free text, click on the Text icon, type out whatever you want and then press enter. To move the text simply drag it around to change its location. Text can be edited and formatted using the text styling toolbar pictured below.
To add a note, click on the Note icon and type out your text. Notes too can be dragged to change positions. To change the color of your note, press the Control key ( ^ ) and click on the note. A dropdown menu will appear with a list of colors.
Difference between Redaction and Annotation
While the Preview app comes built-in with several annotation options that let you draw on top of the PDF, drawing on top of the content does not delete the text from the PDF. For this, you have to use the redaction tool. The redaction tool deletes the text permanently and makes sure that the content cannot be accessed in Preview or any other PDF reader. The annotation tool, on the other hand, makes no such guarantee.
Cropping a PDF
Preview does come with the option to crop your PDF. At first thought, this seems a bit unintuitive as PDFs are not something we generally crop. However, Preview's crop function cannot exactly be used to crop in the traditional sense of the word.
Cropping a PDF in Preview does not delete the contents of the PDF outside the selection, but merely hides them. The entire PDF might still end up being viewable in other applications.
To crop a PDF, you need to select the Rectangular Selection option from the markup toolbar. Once you have drawn a rectangular box on top of the PDF, a crop button will show on the markup toolbar. Click on that, and the page will be cropped to the size of the selection.