You can open a PDF from within the Reader application, from the desktop, or from within certain other applications.
Choose File > Open,
or click the Open button in
the toolbar. In the Open dialog box, select one or more filenames,
and click Open. PDF documents usually have the extension .pdf.
(Windows/UNIX) Choose File > [a previously opened PDF].
(Mac OS) Choose File > Open Recent File > [a previously opened PDF].
To open a PDF attached to an email message, open the message, either by double-clicking the PDF icon or right-clicking/Control-clicking and choosing Open.
To open a PDF linked to an open web page, click the PDF file link. The PDF usually opens in the web browser. In UNIX, you can open the PDF in Reader or save it to the desktop.
Double-click the PDF File icon in your file system.