Juvederm for More Padding in the Ball of the Foot?

There are reports of this being used for different purposes; but, the amount would depend on the individual’s problem. Too much volume could create a pressure effect and make things worse.  See a physician who has a great deal of experience in this matter.

For foot padding, Perlane may be better than Juvederm and here's why
The practice of injecting fillers into the balls of the feet has come about because of the undue pressure from high heels. The filler seems to lessen the associated "my feet are killing me" complaints by cushioning the weight bearing area and taking a little of the pressure off the nerves.
Juvederm is the softest of the hyaluronic acids and I personally think it's tops for lip augmentation. For feet? Well, you may want to consider Perlane which is somewhat hardier in formulation.
If you are on your feet all day long in high heels the length of time any filler would last -- Juvederm, Restylane or Perlane -- is debatable. The HA naturally breaks down in facial areas in 6 to 9 months (longer if you reinject at 4 to 6 months) but for an area that's under mechanical forces such as walking and weight bearing, there's no comparable longevity study. The additional wear and tear should conceivably cause the product to break down faster.
On a side note, if you have proper arch support, the balls of your feet will not take all the beating -- or all the discomfort. So look into adding an arch support if that part of your foot does not firmly make contact with the insole of your shoes.
If you have this done, I'd love to get your personal experience response and I'm sure it would be useful for the patient community too.

With pain from bone spurs in the heel, several patients request a procedure to increase the padding in that area. This is certainly not a common procedure, but has validity. Personally, I have not done the procedure, but would recommend trying a longer lasting filler in the area, maybe even Radiesse. Good luck.

Using Juvederm for padding of the metatarsals or heels is a novel new off-label use.

As we age we lose padding in the foot tissues and adding Juvederm builds up new collagen and provides an extra layer of "protection" for the pounding that has occurred in aging feet. Results are variable as everybody is different. It can break the cycle of pain of heel spurs or metatarsalgia and give long-lasting results. In my own foot, it has been a nice addition to arch supports, orthotics, and extra-padding in my tennis shoes. So far, so good for about 6 months.