Get the car jack out of the trunk and jack away!
I'll start out with one of Newton's laws. For each reaction there is an equal and opposite reaction. Meaning in relevance to this topic. If you jack the ceiling to raise the floor above it, that force is also pushing down on the floor the jack sits on and the rest of the floors underneath the jack. To counter this, you need to support the jack on all floor levels as close to where the jack is located, so the jacking force is concentrated up where you intend it to be.
You can use a bottle jack (which you can find at tool rental stores)and 4X4 lumber, you can nail two 2X4's together, but I don't think they are as strong. I'm assuming you have the floor joists exposed, because I am sure this will crack any plaster/drywall on the ceiling.
It's good to know why the floor is sloped. How did it get this way? Did the joist crack from dry rot or water damage. What condition are they in? If you jack a floor with bad lumber, you may inflict more damage than good. Houses do settle, but if the slope is felt by walking, then something failed over the coarse of the years and you should determine what that was and repair it.(I.E sister or replace the joists)
The jacking part is fun, but realistically you should jack 1/2" or less every few days to allow the house to settle to it's new position. If you jack to your desired height -say 1.25" all at once you will crack walls, perhaps break window panes because the house/floor is moving at a rate it cannot settle fast enough.
You should also find out how the house was framed to get an idea of what potentially else will move when you jack the floor. It's easier to do in a gutted house, but doable in one where the ceilings and walls are still intact.Expect plaster fallout.
Sorry for the windy post. This is just a gist of what you may be getting yourself into.It's important to support the jack on all floors if you want results.
Doug E email@example.com