The "PKDownload Error error 8" is a common error message on Macs, which usually indicates that there was an issue downloading or installing a package or update. Here are a few steps you can try to resolve the error:
1. Check your internet connection: This error can sometimes occur when there is a problem with your internet connection. Make sure your Mac is connected to a stable and reliable network.
2. Restart your Mac: Sometimes, simply restarting your Mac can resolve the issue.
3. Try downloading the package again: If the error occurred during the download process, try downloading the package again from the original source.
4. Clear the App Store cache: If you're trying to download an app or update from the Mac App Store, clearing the cache may help. Open the App Store app, then hold down the Option key and click the "Store" menu. Choose "Clear Cache" and then try downloading the app or update again.
5. Check for software updates: Make sure your Mac is up to date with the latest software updates by going to the Apple menu > System Preferences > Software Update.
If none of these steps resolve the issue, you may need to reach your nearest Apple service centre for further assistance.