On the Settings page, if you drop down the selector, does Firefox still have "Open in Firefox" or your external PDF reader on the list?

Can you remind Firefox of your external PDF reader this way:

(1) after saving a PDF to disk, click the Downloads button on the toolbar (or press Command+J) to use the full downloads list

(2) right-click (or Ctrl+click) the PDF and choose "Open in Adobe Acrobat" (or Preview, or whatever your PDF reader is)

Is that an option?

Thanks for your suggestions.

> On the Settings page, if you drop down the selector, does Firefox still have "Open in Firefox" or your external PDF reader on the list?

Yes, and it works. But it also has "use MacOS default application" and "Use other ..."

> Can you remind Firefox of your external PDF reader this way:

I don't think Firefox has forgotten the external program (Acrobat Reader): if I change the Firefox to "use the default app", or go in and configure it (again) to use Acrobat Reader in "Use other", it works correctly, and remembers that Acrobat is the other. But what it won't do is ask me which I want: open or save. And even after re-specifying Acrobat as the other, it still won't ask properly the next time.

> (1) after saving a PDF to disk, click the Downloads button on the toolbar (or press Command+J) to use the full downloads list > (2) right-click (or Ctrl+click) the PDF and choose "Open in Adobe Acrobat" (or Preview, or whatever your PDF reader is)

I don't even need to right-click: I just click on the file in the downloads list and it opens in Acrobat Reader, correctly. So it seems to know what program to open the PDF with, but something it preventing it "ask"ing.

Is the problem specific to that site? Do you get the three option dialog on other sites? By three options I mean Firefox, external program, save file (screenshot attached).