Updates
The Web Edition keeps itself up to date. The App Store Edition gets its updates from the Mac App Store, like any app from there.
Checking automatically
Once a day, PanoPaper checks for a new version by itself. It never interrupts you with a window: when it finds one, a small dot in your accent color appears beside its menu bar icon, and the menu bar panel shows a row for it - Version version is available, with a line on what the version brings right under it. To read its release notes first, click 'Release Notes…' at the end of that line: they open on the PanoPaper website. Click the row, or 'Update…' at its end, to install it. In the PanoPaper menu, 'Check for Updates…' becomes 'Update to version…'.
A window then shows what's new; install the update and PanoPaper restarts on its own, cameras and all. The row's ✕ - 'Clear' when you point at it - puts it off until the next daily check.
To keep itself up to date, PanoPaper belongs in your Applications folder. Opened from anywhere else, it offers to install itself there - see Troubleshooting.
To stop the daily check, turn off 'Check for updates automatically' in Settings ▸ General ▸ Login & Updates.
Checking now
Choose 'Check for Updates…' in the PanoPaper menu - ⋯ in the menu bar panel, or right-click the menu bar icon - to check right away, whether or not the daily check is on.
What's new
After an update, the menu bar panel shows a row: New in Version version, with a line on what's new right under it. Click the row, or 'Release Notes…' at its end, to read the release notes - what the new version adds, changes and fixes; the row then goes away. Its ✕ - 'Clear' when you point at it - puts it away without opening the notes. Otherwise it goes away by itself after a week.
'What's New in version…' is always in the PanoPaper menu, and the About window has the same notes behind its 'Release Notes' button.