Hmm, Firefox doesn't have a Documents directory. If you need a location for items from your Desktop, I suggest using your regular Documents folder (the one Windows creates for you). To move the documents, you can use Windows Explorer, which I suggest pinning to the Windows Taskbar. They keyboard shortcut is: hold down the Windows key and tap the E key.

Regarding directories in Firefox:

• By default, Firefox saves your downloads to your Downloads folder. You can change that on the Options page if you like: Startup, home page, tabs, and download settings. But Firefox's internal Downloads list will only show what Firefox added to that folder, and not what you moved into the folder from your Desktop.

• Firefox stores your settings and history in a profile folder. If you are interested in the details, please see this article: Profiles - Where Firefox stores your bookmarks, passwords and other user data. I recommend not putting other files in there, as Firefox may occasionally clean the folder and you could lose them.

Overall, Firefox is more oriented toward browsing websites than it is toward browsing files on your computer. Due to security rules and differences in how Firefox integrates with applications, I do not think you will find it to be as useful as Windows Explorer for those purposes.

Next to your post, Question Details > More System Details shows a very old version of the Adobe Acrobat (PDF) plugin.

To update that, I suggest updating your Adobe Reader/Acrobat software. To stay with the "X" series, you can open Adobe Reader/Acrobat and use the Help menu to Check for Updates. That will update Firefox automatically.

If you want to switch to the Adobe Reader "XI" series, you can get it from the following page, but you'll also have to use Help > Check for Updates after installing it because there was a new patch this month that isn't included with the large download. http://get.adobe.com/reader/enterprise/

I do not recommend the new Reader DC version yet.