291
Finally found a fix how to stop firefox downloading each PDF to your local drive
(connect.mozilla.org)
A place to discuss the news and latest developments on the open-source browser Firefox
That sounds like browser.download.start_downloads_in_tmp_dir combined with “open with…”. That setting should download to tmp whenever you open it directly in an application. The other setting (browser.download.open_pdf_attachments_inline) should only be enabled if you want to open PDFs in the browser without downloading them.