Authorised wrong device and now I cannot transfer protected files to ipad

Hello

I have on my apple mac the digital editions files which are protected.  I thought to transfer them I just needed to authorise my iPad mini. So I did this.  Then I noticed that my apple mac was not authorised so when I put my details in it would not let me as I had already authorised another device. 

Can the authorised login be refreshed so I can authorise my mac before I authorise my iPad device? 

The files are my course manuals and I need to be able to view them on my iPad.

Many thanks.

Michie