1.2. Printing Random Pages from Existing PDF
How to pick random pages from a PDF to create new file.
Open original pdf with Preview - ensure that the view is set to 'Thumbnails'
On the thumbnails, click on the pages you want.
Command-click allows you to pick non-continuous pages. When the pages you want are selected go to File - Print.
Set the radio button for Selected Pages in Sidebar
In the bottom left-corner under PDF, click the drop down and choose Save As PDF
This opens a Finder window and you can name and save your pdf file with just the selected pages.