please go to the setting section and reset your browser it will definitely help and improve the downloading speed.

You can try to disable hardware acceleration in Firefox.

• Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available"

You need close and restart Firefox after toggling this setting.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes
• https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

I access a web site that shows PDF icons, to download PDF files. When I click on a PDF icon to display the file, another firefox window will open and the PDF file will start to display on the screen. But the screen populates very, very slow. Some PDF files are less than 200kb in size and may take 5 minutes or more to display on the screen. This happens on no particular web site. All websites react the same. .. If I use Internet Explorer to view the same file, THERE IS NO DELAY, THE PDF FILE WILL DISPLAY ON THE SCREEN IN LESS THAN 2 SECONDS.  ??? ..

Which viewer do you use for PDF files? If you are using the built-in viewer, try the Adobe Acrobat viewer instead. This article describes how to switch that:

View PDF files using Firefox’s built-in viewer

I notice in your "More System Details" that you have two Adobe PDF viewers, a newer version (10.1.8) and an older version (9.5.5). Ideally, to avoid a possible conflict, you should remove or at least disable the older version.

Open the Add-ons page using either:

• Ctrl+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Plugins.

Can you find two entries here and disable the older one by setting it to "Never Activate"?

If the Add-ons page doesn't let you manage them individually, you may need to delete the older plugin from disk. To find its location, try the Plugins page: type or paste about:plugins in the address bar and press Enter. If you search in the page for PDF, can you find entries for both versions of the plugin showing where the old one is?

I did as you suggested. I changed my Adobe plugins to “Never Activate”. I then shut down Firefox and re-started Firefox. I still have the same problem. There is no change in the way the Firefox PDF view responds

Actually, I suggest trying it the other way around. Make sure the most recent Adobe Acrobat plugin is set to either "Ask to Activate" or "Always Activate". Then, in the Options dialog, Applications section, change your PDF preference from Preview in Firefox to Use Adobe Acrobat (in Firefox) -- assuming that choice is available.