Last week a teacher called me and said she was having a bunch of problems with PDF files on her Moodle site.  She said that when she clicked on a link the embedded window showed up but it was nothing but garbage in the window.  If she went to the files area of her site and clicked on the same file it opened just fine in a popup window.  I thought this was very strange as did the teacher.

After a bit of research I found that it was a problem with Adobe Reader and the fact that any version below 9 is not fully compatible with the way XHTML handles embedded documents and that they can't be embedded in frames. There are two solutions to this problem.  The first one is to just upgrade to Adobe Reader 9 which seems to handle this just fine.  The other option is to not embed the PDF files into your page. This second option is probably best for the time being until all of your students get the latest version of Reader.

So, to change the settings in your links:

1. Turn editing on
2. Click on the editing icon next to the link you want to update
3. Scroll to the bottom of the page and find the section called "Window"
4. Check the box next to the "Force download" option.
5. Click the "Save and return to course" button at the bottom of the page.
6. Now check your link to make sure it works.

This simple solution should solve all of your cross platform compatibility problems as well.  Good luck in your continued use of Moodle.