PDF File won't attach to an email using AOL

When I attempt to attach a PDF file to an email in AOL I get the following message.  Any idea on how to fix this problem ?

Please wait...

If this message is not eventually replaced by the proper contents of the document, your PDF viewer may not be able to display this type of document.

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I have installed the "Acrobat Reader DC"  latest version.  I am using a PC with Windows 7