Why does windows 10 stop me opening my pdf documents in Acrobat XI pro?

Having moved to Windows 10 I find that I am unable to open or save pdf on the local hard drive with Acrobat XI pro.  I can store them to an external hard drive and work on them there but not on the local C drive.

I have tried repairing Acrobat to no effect.

It says access denied but the account is a standard user access and even if I make it an administrator account it still cant access the files.

Any suggestions welcome please.