PDF documents can display in Web browsers compatible with Netscape Navigator 3.0 (or later) or Internet Explorer 3.0 (or later). The necessary plug-ins are automaticlly installed when you install Acrobat. If you are unable to view PDFs in your browser before downloading install the plug-in yourself as follows: Windows Open the Browser folder in the Acrobat folder. Copy the nppdf32.dll file to either Netscape Navigator's plug-in folder or Internet Explorer's plug-in folder, or both, if you use both browsers. Mac OS Open the Web Browser plug-in folder in the Acrobat folder. Copy the PDFViewer plug-in to either Netscape Navigator's plug-in folder or Internet Explorer's plug-in folder, or both, if you use both browsers.