Congratulations on the license deal.
There are several ways to get macro pictures. You can buy a macro lens, use extension tubes, or use a closeup filter.
A macro lens is the easiest to use, but it is also the most expensive solution. I'm not familiar with Pentax macro lenses, so I can't recommend a specific lens.
Extension tubes work with your regular lenses. They move the lens further away from the sensor. That allows you to focus much closer. The downside is that while you can focus closer when the extension tubes are on, you can't focus far away. They are cheap and light weight. They work well, but I find them a pain to work with. Because they go between your lens and your camera, you have to get ones that work for your lens mount. Most people I know buy the Kenko brand ones because they are much cheaper than the OEM brands and work just as well.
Closeup Filters are like reading glasses for your lens. You screw them on like a filter. Like extension tubes, they allow you to focus closer than you normally would but you lose the ability to focus far away. Because it is a filter that screws onto the front of your lens, you can get any brand that fits your lens.
I use a 100mm macro lens what I want to go out "macro" shooting. More often, I just throw some extension tubes or a closeup filter into my bag and use them with my normal lenses. It saves space and weight.
If you want to get serious about macro, it doesn't stop with buying the lens. The problem with shooting macro is that it is hard to get enough depth-of-field. In other words, part of your subject is in focus but the rest is out of focus. To get around that problem, you need to use a very small aperture, which means that you end up with low shutter speeds. You can attack that problem in two ways - use a tripod or use flashes. If you do macro with a tripod, I recommend some kind of focusing rail. If you want to use flash, you'll want either a ring flash or special macro flashes.
Don't let me scare you off from macro shooting. You can have a lot of fun with a macro lens or a closeup filter. Like everything with photography, if you really want to get serious about it, you'll find yourself wanting that other gear.