Two versions — pick the one that matches your Mac's chip.
Every Mac sold since late 2020 is Apple Silicon. Every Mac sold before mid-2020 is Intel. Machines from the 2020–2022 crossover could be either.
The very first time you sign in on a new install (Mac or Windows), PIMS pulls your entire dataset — pilotages, ships, swings, library, contacts — down to the device so you can work offline afterwards. Expect it to take 20–30 minutes on a typical connection. You'll see this screen while it runs:
When the download finishes, the same window flips to the done state. Click Continue to PIMS and you're in. Every launch after this one opens instantly and works offline.
What's changed and why, most recent first.