How to flatten files to reduce artifacts from printer drivers

Do you send a file to the risograph machine and the master stencil seems to have mysterious artifacts (lines, fills, boxes of color, inverted images) that you don't see at all in your image? You might have an issue with transparency or gradients being interpreted differently by the printer driver. In general, the solution is to flatten/rasterize everything before sending to the printer driver.

Here are some resources about options for fixing that:

Adobe's tutorial on flattening in InDesign shows you how to export flattened and save presets for exports.
Spectrolite rasterizes separations when PDF mode is off. You can also use the "Clean PDF" tool (in the Tools section) to process PDFs.