WHY are my PDFs showing up in Books?

Single-click any PDF in the FInder. Press option+cmd+i to open a Finder Get Info panel. If the default open application is Preview, do nothing. If not, select Preview, and then click through the Change All… button and its dialogs.

In the Books application, I have two PDFs in its PDFs category. Double-clicking these opens them in Preview.

Apple's Preview is in your Finder Window's Favorites : Applications folder. Right-click on a PDF and choose Get Info. In the Open With section, choose Preview and then click through the Change All button dialogs. This will force Preview to open your PDFs on a double-click.

Command+I would be the preferable choice. Otherwise, you could grab any combination of file types and change them all in one move to be associated with a single app.

That is an annoying difference. Command+Option+I always opens in the panel in the last position you had it. Command+I always starts at the top left and the populates them across the screen for as many items you had highlighted.

I was playing with that more today, and I like your method much better for most uses. You don't have to worry about accidentally having more than one item selected since the Command+Option version will say 2 Items, or however many more than one you have. But will show the file/folder name rather than a count if one item is selected.

Plus the bonus of the palette opening where you last had it instead of chasing it to the top left, and staying on the screen even after a change so you can keep moving from one thing to the next until you choose to close the palette.

I have a different take on it (of course). I can't remember a time where I wanted or needed to open more than one Get Info window. And I don't mind the window opening at the upper-left. However, I guess some people do. 😎

Plain old cmd+i works for me.

Oh cool. I didn't know that. 😎

Notice where the Get Info opens between using a cmd+i and a option+cmd+I. I got tired of it opening in the upper-left corner either above or below my open browser window.

I'm on Monterey at the moment and it opens in the same place.

I get it. If I use cmd option i, I can move it and the next time I use it it remembers the location.

Generally, the only time I use the concatenated Get Info palette is so I can add up the total of a bunch of folders to see what will fit on a 50 GB Blu-ray disk when I'm doing a backup of the NAS.

Makes sense. :)