Can't open Acrobat pdf files in document library - SBS 2011

Question

I've uploaded some Acrobat PDF files to a document library in the companyweb (SharePoint 2010 Foundation website) on SBS 2011. But if I click on one of them in the standard view, acrobat opens and displays a message “The URL you have provided could not be
reached. Please verify that the URL is correct and that the network location is reachable.” I'm using Acrobat Reader XI 11.0.2 and Internet Explorer 10.
I have tried a few suggested solutions, eg to edit the docicon.xml file to include <Mapping Key="pdf" Value="AdobePDF.png" OpenControl="AdobeAcrobat.OpenDocuments"/>, check that the WebClient service is running, and
Use Remote Interfaces permission is set on the SharePoint site. But no luck.
I don't know if this is a problem with SBS 2011, or Acrobat, or Internet Explorer. Interestingly the pdf opens OK in Chrome. It looks like it is trying to edit the document instead of open it in the acrobat reader.
Anyone know of a solution?

Answer 1

I have found one possible solution. In my case the site was brought into Sharepoint Foundation 2010 as a migrated site from a previous SBS installation. 
The site was imported as http://servername and the IIS site had a host header with companyweb so that users could browse to it, and all references to the site were as http://companyweb
All my attempts to open the PDFs were using the http://companyweb URL.
I was researching the issue and had gone through everything, but one thing got me thinking when some sites suggested that I look at the permissive or strict browser file open settings. I looked at the web application and it was set to http://servername in
the Central Administration site. I thought hmm let's try opening the Adobe PDF docs with that URL instead, and it worked!
So I changed the web application URL to http://companyweb and tried again and hey presto it's now working.
I really hope this helps someone, it took me a good couple of hours of my day researching to find the solution here.
Some extra info: we are using Adobe Reader 11.0.6 with IE11. Testing with Firefox worked, but that opens the document by downloading it locally and then using Adobe Reader. fix The above actually resolves the problem, it's nothing to do with permissive or strict
file open settings, I set the SP site back to strict and PDFs still open fine.