Would it make difference if the file is in a different place?
The Full URL used (and its matching PATH) are what you've declared in
Control Panel > Paths & Database > Attachments
Changing this information will have no affect on the real-time URL that is sent to google, except you'll need update directory paths on your server to reflect the new changes.
BTW, you have a typo in your URL. It looks like you have added a backslash where one should not be. Look at your
Attachments > Full URL to Attachment Storage Directory
and remove the trailing slash, so it looks like the example given in the configuration directions.
Here's the URL when I try to preview the pdf in Google Docs:
https://docs.google.com/viewerng/viewer?url=https://www.stovebolt.com/ubbthreads/uploads/attachments//43462.pdf
This could explain why some browsers will correct your error and display the file. while another browser will do exactly what it is told to do, and is presenting you with the error.