I have a garden of Pachysandras that I've never done anything to and had them for over 15 years! The plants barely grow and there are long bent stems everywhere that just flip over. I was wondering if I could mow over it all and hope straight, new vigourous growth emerges from underground and they will once agsin grow straight and be large.

Can I mow late fall, if I wait until spring I have other bulb flowers that might get destroyed if I mow.

They are evergreen, so it's likely that mowing them off will set them back. But they are well established. I would try it on just one section, and see what happens. No matter what, you won't kill them. Don't mow for another month, though, allow them to store as much energy in their roots as possible.

I used to live in the northeast. We would mow the Pachysandra (mower set on highest setting) and use the catch bag. We did this in the springtime just after the last frost date. Once the mowing was done we would manually putt up any weeds (not too many) and any small tree saplings, then applied the Preen pre-emergent and a bit of fertilizer. That's it. Just once a year; almost carefree plant.

I remember that there were several industrious young men who would go door-to-door and offer to prune Pachysandra for a small fee. They were honorable workers and by pruning they were able to have tons of cuttings which they then rooted and sold to others.

Thinking a little more, it might actually be better to mow in the spring. some plants (for instance, Helleborus niger and some Agastache species) are badly damaged if their foliage is cut down in the fall rather than the spring. Perhaps mow some in the fall and some in the spring, and see what happens.

Mowing Pachysandra is not recommended at this time of year. Spring is the best time.
Please check with your local nurseries before you try to mow now.