"always ask before opening this type of file" Check box is not available in outlook 2013 for .pdf attachments

when i try to open a .pdf file from an email (which i do about 20 times a day..!!) it has started asking me if i want to open the file or save it
the checkbox to for "always ask before opening this type of file" is there but greyed out and i cant "untick" it..!!!
can someone help please...
this has only happened recently, they always used to open just fine..!!

Anwsers to the Problem "always ask before opening this type of file" Check box is not available in outlook 2013 for .pdf attachments

As it is a computer wide change, you can change it when you start Outlook as an administrator.
Once you've changed the option, you can restart Outlook normally again.
See:
Do not always ask before opening this type of file

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Another Safe way to Fix the problem: "always ask before opening this type of file" Check box is not available in outlook 2013 for .pdf attachments:

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