How to sharpen a guillotine paper trimmer

Look at your blade - you will see that a cross section of the blade will show a vertical face and a face slanted at about 30 degrees.

You need to use a sharpening tool, such as a honing stone or other sharpening tool along the 30 degree face to clean up the edge which does the actual cutting.

There are scissor sharpening tools which have the exact shape you need for this type of blade. Any decent arts and crafts store should have sharpening tools for this type of device.

These blades can also be removed and sharpened with a belt sander- please be careful and also make sure to not strip the screws when you take it out :-)