I slice up rolls of canvas using a bandsaw, and on occasions a normal wood-working table saw. Now, the edge is not smooth or even, and you need to take off the fluff, the edge of the canvas is trimmed after stretching anyway, so the uneven edge does not matter.
For paper, I think I would make a simple jig, an axle to hold the roll of paper, and another axle with a take up spool, placed about a yard apart. At the appropriate distance from the edge, fix something like a box cutter, and roll the paper through the blade onto the new spool, Then cut the original spool to length, and wind the paper back. If you wanted to try the bandsaw, then you would need a knife blade to cut paper without shredding it. By the time you've done that, plus the cost of the bits if you have to buy them, it would probably be as cheap to get a wider printer
Best wishes,
Ray