This problem is not unique to Macs! Hope this helps:
Some students and Mac users in particular will report from time to time that they are unable to open a PDF file that has been posted to Blackboard. There are a couple of simple fixes:
- Rename the PDF and file and repost.
In some cases, PDF files can become corrupted either during the Adobe file writing process or when it is posted. Students then receive an error when they try to open the file. Renaming the file to a new name and re-posting to Blackboard usually fixes this issue.
- I did this, but the file will not open for Mac users. What else can I try?
If students are using their own personal Mac computer they can change the default program that opens a PDF file from Preview to Acrobat. This may allow them to open the file when downloading it from Blackboard. Please contact the help desk for assistance in changing your preferences.
Also from another Website:
Known Issue: Students using Safari and Firefox on a Mac
Users are not able to view .pdf files in Content Areas added using the Build Content > File option. They receive a plugin missing message. Workaround: Instructors should use the Build Content > Item button to add .pdf files to Blackboard content areas. Files added in this way will open in an external program such as Preview or Adobe Acrobat Reader.
This is actually an issue unrelated to the one in this discussion.