Crop or rotate a PDF in Preview on Mac
You can crop a page to hide content, or rotate it to change its orientation.
Crop a PDF
To crop a PDF, you first select the area you want to keep, and then discard the rest. If you want to view the dimensions of the content you’re selecting, choose Tools > Show Inspector, then click the Crop Inspector button 
and choose a unit of measurement that’s displayed in the Crop Inspector window.
In the Preview app
on your Mac, click the Show Markup Toolbar button 
(if the Markup toolbar isn’t showing), then click the Rectangular Selection button 
.Select the portion of the page you want to keep.
Click the Crop button in the Markup toolbar (or use the Touch Bar).
Note: To undo the crop immediately, choose Edit > Undo Crop. To undo the crop later, return to a version before the crop. Choose File > Revert To > Browse All Versions, then browse the versions to restore the one you want.
Rotate a PDF
In the Preview app
on your Mac, open the PDF you want to change.Do one of the following:
Rotate one page: Click
(or use the Touch Bar) to rotate the page to the left. Continue clicking to keep rotating.To rotate a page to the right, press and hold the Option key and click
until you’re done rotating the page.Rotate several pages at once: Choose View > Thumbnails or View > Contact Sheet, select the pages to rotate, then click
to rotate the pages to the left.To rotate the selected pages to the right, press and hold the Option key and click
until you’re done rotating the pages.