Split view with 2 pdf files opened with Finder

I opened two PDFs in separate Preview windows. When you press and hold the left PDF window's green traffic light, you select The window to the left of the screen option. The left half of your screen is now that left PDF. The other PDF window shrinks, gains a blue border, and you click once anywhere inside that window. There will be a brief pause, and then that window expands to fill the right-side of your screen.

It is macOS Monterey, and you can split-screen two different PDFs open in Preview. In the first open PDF, click and hold the green traffic light in the title bar of its window and select Left. Then, on the other open PDF window, just click on its green button and now you have two split-screen PDF open. Tested: macOS 12.1.