Skim Highlighting sections of a PDF document

You can highlight interesting or important parts of a document. You can enclosing them in a red oval or a green box. Or you can highlight, underline or strike out text.

The highlights are saved with the document, so also other Skim users can see them. The highlights are not saved in the PDF data itself, therefore other PDF viewers will probably not be able to show the highlights.

To highlight a section of a PDF document:

  1. Choose Tools > Text Tool.
  2. Select the text you want to highlight.
  3. Choose Notes > Circle, Notes > Box, Notes > Highlight, Notes > Underline, or Notes > Strike Out.
  4. You may drag circle and box highlights in the document until the highlight is located where you want and has the size you want.


  1. Choose Tools > Note Type > Circle, Tools > Note Type > Box, Tools > Note Type > Highlight, Tools > Note Type > Underline, or Tools > Note Type > Strike Out.
  2. Select the text you want to highlight or region you want to circle. You can do this repeatedly.

You can also use toolbar buttons to add highlights. To add highlight buttons to the toolbar, choose View > Customize Toolbar and drag the buttons to the toolbar.

You can edit or delete the highlights. To change the color used for the highlight, choose Tools > Show Colors. To delete the highlight, choose Tools > Text Tool or Tools > Note Tool, select the highlight, and press Delete.

Circle and box highlights can also be moved and resized. To move or resize the highlight, choose Tools > Text Tool or Tools > Note Tool, and use the mouse. Drag the black box to resize.

See also

Adding notes to a PDF document  
Adding lines to a PDF document  
Changing the color for notes and highlights