Hi, see if making any adjustments here helps : https://support.mozilla.org/en-US/kb/applications-panel-set-how-firefox-handles-files

Thank you very much for your prompt reply.

After much time wasting experiments I managed to download the PDF file through Opera Browser version 53.0.2907.68. I had never used this browser before. Google Chrome would not download the file either. All I can deduct from this is kinda weird. Firefox will not also (for some considerable time - many months and different versions of Firefox) download MP4 files.

Go figure that one.

Are you sure the file itself was properly formatted as pdf file? That can also cause Browser to reject the download as well. To be sure open the pdf before downloading to verify the Browser can see the file.

Thank you. I had already thought of that option. The file itself was properly formatted as a pdf file. I am able to open it (and other PDF's) up in the firefox preview mode. It appears to have the same common problem with MP4 files attachments I have mailed to me which also will not download. I tried numerous methods before my initial posting, which included "always ask", "save file" in Tools - Options. I even disabled a small number of permanent add-ons at the same time which I had used for a long time. None of these alternatives worked. Frustration personified. Motto: don't give up!!

SAFE MODE

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

In Firefox Safe mode these changes are effective:

• all extensions are disabled (about:addons)
• default theme is used (no persona)
• userChrome.css and userContent.css are ignored (chrome folder)
• default toolbar layout is used (file: localstore-safe.rdf)
• Javascript JIT compilers are disabled (prefs: javascript.options.*jit)
• hardware acceleration is disabled (Options > Advanced > General)
• plugins are not affected
• preferences are not affected

TEST''''is issue still there ?

Can try this if the above is not the issue : uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files , C:\Program Files(x86) & C:\ProgramData Then restart system. Then run Windows Disk Cleanup. (Note: This should be Pinned and run Weekly, If never done below expect 10's of gig's) Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved. But you should make a back up before you do :

• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

Reinstall with Current Release Firefox 60.0.2 with a Full Version Installer

• https://www.mozilla.org/firefox/all/

Please let us know if this solved your issue or if need further assistance.

PK Shadow, Thank you, again. I had already been through many options including uninstalling my (the) current version, 60.0.2, 64 bit Mozilla Firefox. I tried installing and uninstalling five old Firefox versions including version 55.0. This also included checking Program Files, ProgramFiles(x86) and Program Data folders to see if the Windows Uninstall method had performed correctly.

Together with enabling and disabling a small number of permanent add-ons on each occasion which I had used for a long time. None of these extremely time consuming alternatives worked. Even "The Refresh Firefox feature" did not work. I managed to download a very important business PDF file through Opera Browser version 53.0.2907.68. Unfortunately this browser is also illustrating the same problem with PDF's and MP4's. I will continue to seek the right answer/s somewhere.... Cheers.