How to crop a lot of pages in preview

In Mac, you may use Preview to crop many margins down in order to have a multi-page PDF with large margins on each page.
You must be sure that your sidebar is visible and let it display thumbnails with the button at the bottom when you Preview the PDF.

Step 1

You may change to the select tool by using the toolbar button, the Tools menu or pressing Command-3.

Step 2

Drag a box around the area you want to keep, and press the sidebar, cllick Command-A to choose all pages.

Step 3

If there are some pages with different orientation (for example, landscape), hold Command and press these pages to de-select them.

Step 4

In the final step, under Tools menu, select Crop, or more simply, press Command-K.