Chrome. Under When Visiting Other sites, in the drop-down list choose Allow Always and click Done. On Mac OS, it’s already there. Select Adobe Reader in the list of plug-ins. Select the text you want to highlight, then click the highlight icon that appears below your selection, or right click to find the highlight option in the context menu. In addition to the built-in PDF viewer, Firefox offers the option to utilize the Adobe Acrobat Reader plugin for opening and interacting with PDF files. Go