Tips_and_Tricks
The Preview shortcuts are Option + Arrow Up/Down, so Skim is not really consistent there. Option + Arrow Up/Down also works in Safari, and the Help viewer for macOS apps (including Skim). Maybe that's a good alternative?
I guess these shortcuts do serve a purpose when zoomed in - then they move through the pages where as the page up/down keys will scroll an amount based on the viewport height. Still, I have changed the shortcuts on my system to use the same as Preview: Option + Arrow Up/Down
Consider changing or removing keyboard shortcuts for previous & next
Tips_and_Tricks
Missing menu item: Use Current View Settings as Default
I would have loved to have seen this, for example by supporting selecting multiple pages in the thumbnails side panel or overview.
REQ: Support macOS document features in toolbar