TOPIC:

if i purchase the software so how many users can use the one login?
secondly if i reinstall the windows in our system then how we can reuse the same purchased software as we just need to put login or is there any restrictions on it.

According to our license agreement, a Find my Font Pro software license can be used by a single user. It is permitted to install the software on second computer and use it as long as it is not used at the same time as the first. An example would be one computer at the office and the second one at home.
See this post for more details.

If you reinstall Windows you must re-activate your license.
You can find more details on this topic category .

Please let me know if you need more details.