do changes in /etc/security/limits.conf require a reboot?

No but you should close all active sessions windows. They still remember the old values. In other words, log out and back in. Every remote new session or a local secure shell take effect of the limits changes.

Apply the changes directly to a running process if you have prlimit installed (comes with util-linux-2.21)

prlimit --pid <pid> --<limit>=<soft>:<hard>

for example

prlimit --pid 12345 --nofile=1024:2048

Refer here

To temporarily set the open files limit for the user you are currently logged in under (e.g. 'root'):You can also use the ulimit command to change the values in your current shell. However, hard limits can only be adjusted downwards unless you're root.

Example:

# ulimit -a
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 62449
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 10240
cpu time               (seconds, -t) unlimited
max user processes              (-u) 1024
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

To change the nofile to 94000 you can do:

ulimit -n 94000