The most common backing paper is just a roll of brown kraft paper used for packing. We dont sell it but it is commonly available at most office supply stores and moving supply stores. It's primary purpose is to keep dust out of the picture frame and provide a clean finished look to the framing package. You can use glue, atg tape, or standard double sided tape to apply it to the back of the wood picture frame. Since it only makes contact with the back of the wood frame and the wood frame is already acidic you dont really have to worry about archival issues. Your artwork should be buffered from the wood frame and the backing paper by the mat and a frame backing such as acid free foamcore.
Originally Posted by rtbadman