'pdftopdf.filter Will Damage Your Computer' Error

It can be quite distressing when your normal activities on your Mac device are disrupted by the sudden appearance of a warning prompt stating that 'pdftopdf.filter Will Damage Your Computer.' Before you go scrambling to contain the supposed damage, take a deep breath, and check if you have an HP printer connected to your Mac. If this is indeed the case, you may have found the culprit behind the scary message.

In their efforts to stop the spread of dubious or sometimes threatening applications within their ecosystem, Apple has introduced more and more security measures continuously. One of them is called Gatekeeper and its purpose is to make sure that only trusted applications are present on the system. One of the methods it uses to ensure the validity of the applications is to scan their security certificates. However, sometimes even legitimate applications and drivers can be flagged due to expired or compromised certificates resulting in the '[App] will damage your computer' warning message.

This could be the exact reason behind the pdftopdf.filter error, as HP 'unintentionally revoked credentials on some older versions of Mac drivers.' To fix the issue, users should uninstall their printer devices and the associated drivers, and then install the latest driver versions released by HP. 

1. Start by deleting the /Library/Printers/hp folder
2. Go to 'System Preferences' and choose 'Printers and Scanners.'
3. Delete the printer devices available there. 
4. Install the latest HP drivers.
5. Add your printer back by going to 'Printers and Scanners' again and clicking the '+' button. The printer will usually be listed under 'USB.'

You also can allow macOS to install the required drivers. After deleting the folder and removing the printer, connect it back to the Mac via USB. You should see a prompt asking you to approve the download and installation of a suitable driver. 

Alternatively, you can use the AirPrint feature that was introduced by Apple. If your printer supports AirPrint, you can start printing documents and pictures without the need for any drivers.