Black background

I think you could do that, but I'm describing X6 so you may have to make some adjustments for X5:

• Create a new document 
• Go to Layout > Page Background and choose the option solid, colour black, print and export bitmap, click OK
• Back in the document, make sure nothing is selected, go to the colour palette and left click on the white square. Select all the "change document defaults" options, click OK
• Go back to the colour palette and right click on the white square. Select all the "change document defaults" options, click OK
• Go to tools > save settings as default if you want this to be your default for future documents too.

This allows you to edit with the default as white on black.

Then when you print go to the prepress tab and select invert in paper and film settings, so that it prints as black on white,

There is a limitation with this method: if your design page is smaller than your printer page, the area outside the page will print as black. You can fix that by adding a large, locked, black rectangle behind all your objects.

This works, but on my printer the white is coming out slightly grey. So you may need to experiment with colour management (possibly, turn it off) to get the best print using this method.

Try it with some simple documents first, in case the results are not what you expect. And remember that there will be limitations -- for instance, you will probably not be able to export to other formats using this method.