TIL this about #Firefox in private browsing mode:
> If the PDF is opened rather than saved, the downloaded file is considered temporary and will be deleted at the end of the private session. You need to manually save the PDF for it to be preserved. [1]
Well-intentioned, but rather counter-intuitive since it shows the file as both downloaded and stored in a specific location. Seems like at minimum the PDF viewer should display a warning banner.