Short answer

In principle, you can. But you should imho not use PlantUML for static diagrams. Read the longer answer below for an explanation.

Longer answer

We really encourage the use of PlantUML for sequence diagrams (see question F-9 (Tools for sequence diagrams)), but don’t like it for static diagrams.

That’s because in static diagrams we propose to carefully layout your building blocks, so that important elements are focussed, or elements somehow belonging together are drawn close to each other.

In PlantUML you can give formating hints, but the autolayout algorithms decide for themselves wether they can apply your suggestions or ignore them.

I (Gernot) tried PlantUML numerous times for static diagrams in real-world situations - and was always really unhappy with the results (although I really like it for sequence diagrams).