Here are some ways to zoom in and out:
To zoom in or out, choose View > Zoom In or View > Zoom Out.
To see the image or page in its original size, choose View > Actual Size.
To view an image or page at a size you specify, resize the Preview window to the size you want, then choose View > Automatically Resize. The image resizes to fit the window size.
To zoom to a particular section of a PDF document, choose Tools > Select Tool, select the section, and then choose View > Zoom To Selection.
To see a page at a specific percentage of its original size, type a percentage in the Scale field in the toolbar.
If you don’t see the Scale field, choose View > Customize Toolbar.