I have imported several custom symbols from SVG files. These appear fine at high zoom levels in yEd but seem to print out (or export to PDF) as low-resolution images. The same thing occurs with the built-in SVG symbols. Example:
Exported PDF: http://www2.gi.alaska.edu/~cpbruton/documents/yed/print_example.pdf
Screenshot of zoomed-in area in yEd: http://www2.gi.alaska.edu/~cpbruton/documents/yed/print_screen.png
And here is a screenshot of the exported PDF opened in Preview:
Note that all the text and lines look good, and the FGRplus (grey rectangle) looks good. The remaining symbols are blurry. The same thing happens when I print directly. I am using yEd 3.9.2 on Mac OS X 10.6.8.