I do that by “printing” one PDF page from the original. See “print” dialog box.
Edit: from subsequent posts below (Thanks!) learned that showing the PDF in Preview, then can simply “drag and drop” to a folder or desktop. New to me (after decades of Mac use). Muscle memory.
Jim, Cmd-C / Cmd-V is great for the old farts with some esssential tremor ha ha ha (just to make sure, I am referring to myself). These days, drag and drop is mostly for getting up in the morning and going to bed at night.
hahaha!
I had many years on Windoze (and still keep a laptop for random support needs) so I know the drill but on a Mac, it’s drag and drop all the way for me. In fact, it’s the first thing I try in many scenarios.