Works on paper are held to a higher standard than paintings. 

Reasonable levels of restoration to a painting may not have a negative effect whereas, staining, toning, foxing, trimming, tape residue, gluing, fading, wrinkling and other factors will destroy the value of a print.  Never purchase a print already framed as it could have many or all of those negative conditions as previously mentioned.  When you have the print framed or decide to reframe any of your works on paper, insist that archival materials be used such as acid free matting, acid free backing and linen hinges with mulberry paste as an adhesive if necessary.  UV blocking acrylics will help block the damaging light rays and strategically placing the works away from strong sources of light will also preserve your art.