open a PDF or image
You can open pdfs and image files several ways in Preview.
From the desktop: Double-click a PDF or image file; it opens in Preview by default. You can also select a file or files, then choose File > Open With > Preview.
From within Preview: Choose File > Open, locate and select the file or files you want to open, then click Open.
To open a file you’ve worked on recently, choose File > Open Recent.
From iCloud: Click iCloud Drive in the Finder sidebar, then double-click the PDF to open it. For more information about working with files in iCloud, see Use iCloud Drive to store documents.