Hi there! It seems you're experiencing an issue with PDF Gear not responding to the Quit command on your Mac Mini M1 running Sequoia 15.4.1. Let's see if we can resolve this together!

First, could you let me know if PDF Gear becomes unresponsive consistently, or is this a one-time issue? Also, have you tried any specific troubleshooting steps so far, like force quitting the application or restarting your Mac?

While I wait for your response, here are some general steps to try:

1. Force Quit PDF Gear:
- Click on the Apple logo in the top left corner of your screen.
- Select "Force Quit."
- Find PDF Gear in the list and click "Force Quit."

2. Restart Your Mac:
- Sometimes a simple restart can resolve performance issues. If you haven’t done this yet, please give it a try.

3. Check for Updates:
- Make sure you have the latest version of PDF Gear. Open the app (if you can) and check for updates within the app settings, or visit the PDF Gear website to download the latest version.

4. Look for Known Issues:
- I've found that some users are reporting bugs with macOS Sequoia 15.4.1 that can affect application performance. You may want to visit this discussion for more insights on similar issues.

Please try these steps and let me know how it goes! If the problem persists, we can explore deeper troubleshooting options.