I do it all the time and in fact just cut down a roll of smooth pearl this morning to give me a bunch of nominal 8" stock.
I too use a 12" chop saw with a fine blade and then sand with a 9 inch disk/belt sanding machine using the disk sander with a fine grit.
Just tape the roll securely with packing tape at several points and run one piece of tape the long way to seal the edge. Depending on the size of the saw and roll of paper you might have to turn the roll as you are cutting. I clamp a strip of wood to both the saw and sander tables to make it easy to spin the roll exactly perpendicular to blade or sanding disk. Cut the piece a 1/32 of an inch or so oversize and then sand smooth.
Make sure you blow all dust off the roll and discard a turn or two on the roll. You don't want any of the dust getting in your printer.
I have done this with many types of paper including enhanced matte, smooth pearl, premium luster, semimatte, and a water colour paper from inkjetart with excellent results. I did one roll of canvas and had trouble with fraying on the edge -- I would not recommend cutting down canvas.
Good luck.........
Doug