There are several other remedies to try listed below link.... https://libanswers.brunel.ac.uk/faq/13724

No solution. That page deals with: o Adobe Reader. I'm trying to use MacOS Preview o File doesn't open. For me, it opens, but leaves a

 track in ~/Documents.

Thanks, gil

A PART file is a partially downloaded file from the Internet used for downloads that are in progress or have been stopped. Some PART files can be resumed at a later time using the same program that started the download. PART files are typically used by Mozilla Firefox and several file transfer programs, such as Go!Zilla, eMule, and the discontinued eDonkey program. More Information

If you are using Skype on a Mac and a PART file keeps reappearing, move the file to the trash and make sure it's the only file in the trash. Then, right-click the "Trash" icon, hold the "Command" key, select Secure Empty Trash, and verify that the trash is empty. Now, when you reopen Skype, the PART file should no longer reappear.

NOTE: To resume a PART file download with FlashGet, you may need to rename the extension to .JC.

In my case there is no "downloaded file from the Internet". It's a local PDF, accessed by a FILE:// URL. I see no need for Firefox to prepare for a "partially downloaded file". In addition to your suggestion, I often remove the .part with no threat to other content of Trash by dragging their icons to Terminal "/bin/rm ".

Thanks, gil

I don't think that Firefox would leave a .part file as a file with this file extension would be of no use. The presence of a .part file might be an indication that you have security software that is locking the file and prevents Firefox from removing it. You would normally a .pdf file in the OS temp folder to pass it to an external application.