I highlight text in my browser's PDF viewer but when I send the file to a friend the highlights are gone. How do I keep them?

The highlight needs to be saved into the file.

Adobe Acrobat Reader: open the PDF, choose Comment, then the Highlight tool, mark the text, and use File > Save. The highlights are saved as annotations.

Browsers: Edge lets you highlight and then Save or Save as to write the changes into the PDF. Chrome's viewer can not save highlights, so use another viewer for this.

Mac: Preview supports highlights through the Markup toolbar and File > Save.

If someone still does not see them, they may use an app that hides annotations. Ask them to open the file in Acrobat Reader.

Saved from Edge and my friend sees the highlights. Thanks.