I see that the pool contains frames (A4, A3, etc), but I can’t figure out how to add one to a schematic page.
I’m probably missing something obvious, but anyone mind pointing it out for me?
ps. Very much liking Horizon so far, even creating a somewhat complex part/package from scratch 
Open the schematic properties dialog (it’s in the hamburger menu) and select the sheet you want to modify. In there, you can set the desired sheet.
Where else did you look? Perhaps it’s worth also adding other ways to invoke this dialog so more people find it.
Thanks!
The first place I looked was in the space bar menu, searching for “frame”. I think I had look in the properties, but overlooked it.
I searched the docs, too, but nothing came up. I’m not convinced that adding a frame needs to be added to the spacebar menu, but a quick mention somewhere in the docs would be helpful I think.