Hi Matthias,
To add specific styles on a page basis start with adding a Custom Body CSS Class via the Page Settings.
Then add your class to your skin style like this:
.my-custom-page-class p {
font-weight: 700;
}
The only other option is to use a different skin for that page, but that seems like overkill for your example.
Hopefully this gets you running in the right direction.
Elijah