I create my diagrams in Enterprise Architect. Sometimes I need to embed them in Power Point presentations but it does not look good in the UI as it would if I would write them there from scratch.
Is there a way to do it nicely? Which tools would you recommend to manage a long persisting architecture and also present it nicely in presentations?
EA is for making models - more functional that "pretty", so it sounds like your using the wrong tool for the job. However, I've been in the same boat - so I know exactly what you're talking about!
Other possibilities...
Make dedicated "pretty" diagrams where necessary, and leave the more "serious" ones for the "real" work. this might not be so viable depending on the size and complexity of the models (and the rate of change).
Get a better tool.
Give the raw diagram to someone like a designer and get them to do you a new "pretty" one.
Apologies that this is a bit off tangent, but I've always wondered what percentage of EA like modelling tools get used properly through a project.
Of the instances I've used it was difficult to keep full round-tripping going and it was more used as a conceptual architecture tool to get the message across to the team. So a diagram tool with organized files normally work fine and gets my pretty diagrams.
@Adrian what do you term as 'real' work here?
I strongly recommend the use of diagrams/UML as a communication tool as opposed to specifications (see http://martinfowler.com/bliki/UmlMode.html and http://fragmental.tw/2008/11/07/trying-to-write-architecture-specs-that-dont-suck-much-part-i-the-spec/).
That said, I often have to present diagrams to a larger audience using PowerPoint or Keynote slide decks. In presentations it is very important to keep in mind what the public you are presenting to already know about the architecture and technology and what to you want them to understand.
If you present to a group of executives the message has to be abstracted and probably your diagrams should use a very simple notation of boxes and arrows. If you are presenting at your local user group you probably can use more semantic constructs in your diagrams --like aggregations and inheritance-- but you probably will need to abstract-out most of the things that are specific to your company and people from outside don't know about (e.g. replace a module called "XPTO 1.0" with "Legacy Billing System").
Once you know what level of detail you should use you can get a tool. i'd recommend simple diagram tools like OmniGraffle or Visio. If you want more UML features than those tools provide you may try JudeUML, it creates quite clean diagrams that can be easily edited in a proper graphic editor.
I also recommend Dan Roam's "The Back of the Napkin" ( http://amzn.to/c5khDx ). It's a very interesting book on how simpler graphic models can be effective.