Cannot access web PDF files

Question

I am using an iMac 27 inch mid 2010 with OS 10.9.4 and Safari 7.0.5, processor speed 2.93 GHz, Intel Core i7, 8GB 1333 Mhz DDR3.
When I try to view a PDF file on the Internet using Safari I get an error message that says "Before viewing PDF documents in this browser you must launch Adobe Reader and accept the End User License Agreement, then quit and relaunch the browser". This error message occurred when I used Safari 7.0.5 and also after updating Safari to 7.0.6. Normally, I do not have the Adobe Reader open prior to viewing a PDF file on the Internet but, just in case that was a problem, I opened Adobe Reader version 9.5.5 or 10.1.10 prior to opening either version of Safari and got the same error message. 
However, if I used Firefox 29.0.1 browser I could view the PDF files and copy them to my iMac. Also the Adobe Reader versions 9.5.5 and 10.1.10 will both open local PDF files from my iMac. Prior to updating the OS to 10.9.4 and Safari to 7.0.5 there was no problem opening PDF files over the Internet with Safari 7.0.4 and OS 10.9.3. So, from this I deduce that Adobe Reader is not the source of the problem and that there is something wrong with Safari 7.0.5 and 7.0.6.
My initial thought was to run Repair Permissions from the Disk Utility but this made no difference. Also the error message does not make sense as you have to accept the End User License Agreement when Adobe Reader is installed and there is no obvious means of accepting the License Agreement again when the Reader is launched after it has already been installed.
Can you help.

Answer 1

Back up all data before making any changes. Please take each of the following steps until the problem is resolved.
Step 1
If Adobe Reader or Acrobat is installed, and the problem is just that you can't print or save PDF's displayed in Safari, you may be able to do so by moving the cursor to the the bottom edge of the page, somewhere near the middle. A black toolbar should appear under the cursor. Click the printer or disk icon.
Step 2
There should be a setting in its preferences of the Adobe application such as Display PDF in Browser. I don't use those applications myself, so I can't be more precise. Deselect that setting, if it's selected.
Step 3
If you get a message such as ""Adobe Reader blocked for this website," then from the Safari menu bar, select
          Safari ▹ Preferences... ▹ Security
and check the box marked
          Allow Plug-ins
Then click
          Manage Website Settings...
and make any required changes to the security settings for the Adobe PDF plugin.
Step 4
Triple-click anywhere in the line of text below on this page to select it, the copy the selected text to the Clipboard by pressing the key combination command-C:
/Library/Internet Plug-ins
In the Finder, select
          Go ▹ Go to Folder
from the menu bar, or press the key combination shift-command-G. Paste into the text box that opens by pressing command-V, then press return.
From the folder that opens, move to the Trash any items that have "Adobe" or “PDF” in the name. You may be prompted for your login password. Then quit and relaunch Safari.
Step 5
The "Silverlight" web plugin distributed by Microsoft can interfere with PDF display in Safari, so you may need to remove it, if it's present. The same goes for a plugin called "iGetter," and perhaps others—I don't have a complete list. Don't remove Silverlight if you use the "Netflix" video-streaming service.
Step 6
Do as in Step 4 with this line:
~/Library/Internet Plug-ins
If you don’t like the results of this procedure, restore the items from the backup you made before you started. Relaunch Safari.