You sure can! A number of girls and women like to wear pads during their periods and wear an extra thin pad made for everyday wear between their periods. These are called panty liners. They help keep your underwear clean and are much easier than underwear to change in the middle of the day.  Choose one that is unscented to avoid irritation from frequent use. Follow the package instructions for changing recommendations.

As long as you change them regularly, you can definitely wear pads all the time. I'm just not sure why you would want to. If you're having a little bit of discharge or breakthrough bleeding in between periods, you might want to try using a panty liner to manage that. Liners are much thinner, so you may find them more comfy for day to day use.

Pads can be worn whenever, either on or off your period. They can be used as back-up support for those times when you're uncertain about the day you're period is going to start. I, and a lot of other girls, like being one step ahead of our period -- saves us from having to replace a pair of panties. When equipped with a "just in case" pad, you can feel a lot more comfortable about wearing underwear you really like. You won't have to resort to some second-tier pair of granny panties because you're scared to stain any other decent pair. If you're using them for any sort of bladder issues, menstrual pads will not do the trick quite as well as pads made specifically for these issues.