To highlight text in a PDF, you can use a PDF reader or editor. Here are the steps on how to do it using Adobe Acrobat Reader:

1. Open the PDF file in Adobe Acrobat Reader.
2. Click on the “Comment” tool in the toolbar.
3. Select the “Highlight” tool.
4. Drag the cursor over the text that you want to highlight.
5. The text will be highlighted in the color of the highlighter tool.

You can also change the color of the highlighter tool by clicking on the dropdown menu next to the highlighter tool.

Tips for highlighting text in a PDF:

• You can also use a PDF editor to highlight text. PDF editors typically have more features for highlighting text, such as the ability to change the thickness of the highlight.
• If you are highlighting text in a PDF file that is password-protected, you will need to enter the password before you can highlight the text.
• If you are highlighting text in a PDF file that contains scanned text, you may need to use an OCR (optical character recognition) converter to convert the text to a machine-readable format before you can highlight it.
• Save the highlighted PDF file with a different name to avoid accidentally overwriting the original file.