enable text access for screen reader devices for the visually impaired

[rw@molprod.com]

On a document properties, security tab and below the options for setting passwords, there is a check box for "enable text access for screen reader devices for the visually impaired" but this is greyed out and cannot be selected?

[rw@molprod.com]

Have since uninstalled and reinstalled but the option to select is still not possible. Yes I an selecting the 'Require a password to change security settings.....' check box first which should then give the option for the enable text access check box.