Use your paper cutter long enough, and it will eventually grow dull. A dull blade will not cut through paper as efficiently, if at all. Cheaper brands may only need a blade replacement, but guillotine cutters and rotary paper cutters with a self-sharpening system will need to be resharpened. Cutting materials other than paper, such as plastics, paper clips, metal and laminated sheets, can speed up the time in which the blade grows dull.
Determine whether the blade needs to be resharpened or replaced. Throw away the blade if the paper cutter is a cheap, low-end brand and replace with a new blade. Have a spare blade around just in case.
If the paper cutter is a higher-end model with a blade that can be resharpened, take out the dull blade and replace with a sharp blade to keep the paper cutter usable. Do this cautiously as to avoid injury.
Find local facilities that can sharpen blades, such as a hardware shop. Also try going to a barbershop or salon to have the blade sharpened. Salons have equipment for sharpening their scissors and blades, which can also be used for your paper cutter blade.
Use a honing stone or other sharpening tool at your disposal. Hold the blade at a 30-degree angle and slide the blade clean up the edge. Sharpening tools can be bought at art supply stores or craft stores.