We need to cover an old logo on an exterior, coroplast sign. Will this material blockout something already printed? Thanks for your help.

The Weatherproof Polyester for Laser is not intended to block out but depending on your design, it may work for you. Our Blockout for Laser is a coated white matte with an opaque gray backing that will cover text or images it is placed over. This material is not weatherproof, however, and only available in the 8.5" x 11" sheet size. The Clear Gloss for Laser is a weatherproof material and is sometimes used by customers as a laminate or overlay to protect a non-weatherproof material against moisture and other contaminants. If you would like to try samples of these materials, you are welcome to request a few sheets for free by visiting the link below. https://www.onlinelabels.com/samples

Is this a permanent adhesive? Or will it remove nicely if need be?

Our Clear Gloss Laser (CL) does feature a permanent adhesive which would leave residue behind once removed. However, we do offer the following article on the different ways to remove label adhesive: https://www.onlinelabels.com/articles/how-to-remove-labels-sticker-residue .