When I try to export my diagrams in jpg format, they are in low quality. How can I improve the quality of the graphics for printing?
I would suggest using either the SVG or PDF export options, because they are a vector format and will scale nicely. In the case of SVG you can use a web browser to print the diagram. Inkscape is also a nice option for printing and modifying exported SVG files http://www.inkscape.org/
There are some suggestions here if you need a really big diagram:
http://superuser.com/questions/161313/print-a-huge-svg
Peter
Thank you for the answer. Indeed inkscape is really good to do this kind of work. It worked perfectly!