In addition to the other suggestions, I use archival tape for torn pages in manuals. It is very inconspicuous and sticks to paper very well. The kinds I use are Lineco Document Repair Tape (1" wide) and Lineco Transparent Mending Tissue (0.5" wide). After repair I keep the manuals in heavy ziplock bags and use a copy printed from a scan if I need to refer to something. For the accessory boxes, I have also used archival tape if there are minor tears to the cardboard, but for the most recent repair I covered the box in printed scrap-booking paper to encase the sticky duct tape from another's prior repair. It looks (an works) a thousand percent better than it did before. I will make a replacement lid for the box from card stock and then wrap it in the same paper. This box was almost ready for the trash can so I had no qualms about tampering with the original condition.