We use our own Paginator to print the diagram, which can be used with any UIElement. I make use of the DocumentPlane to paginate the graphic.
Unfortunately, the print output is always blurry, and it doesn't make any difference when I replaced our paginator with the DiagramPaginator.
This is an issue which is annoying me for a long time. Today, I had an interesting discovery:
In Mole, a WPF Debugger Visualizer (I hope it is familiar to you) which is able to display the visual tree, the preview for the DocumentPlane has a similar blur like the print output we get, while any other Visual previewed with Mole is displayed adequatly.

It would be very helpful if anybody has an explanation for this phenomen. It certainly relates to the problem we have.

My assumption is that while using VisualBrush's (like  it's done with Paginator), something special has to be considered in order to have a clean output. And I'm sure that the Mole Debugging Visualizer actually uses a VisualBrush in it's preview.

Here's a screenshot of the Visualizer with the DocumentPlane:


and here as the content of our scrollviewer

Unfortunately, that doesn't affect anything. Besides, the blur can't be a product of the commong device pixel overlapping problem.

On the first line, every clue why the graphic differs is helpful. "Mole for Visual Studio" uses a VisualBrush or RenderTargetToBitmap, similar to printing the diagram.
The Mole Developers don't know anything, because the problem manifests itself for the first time only with the Mindfusion Diagraming Component.

So any hint about this problem automatically helps me resolve our print problem, which seems to be related