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As part of our Autodesk University 2006 presentation on "What DWF Can Do For You?" Brian Mathews noted that by default DWF files are published with the same security as physical paper. As such, the DWF files are published at a relatively low DPI - 1200. To improve the precision of your DWF files, particularly for electronic measurement, you want to use a higher DPI. For AutoCAD, this setting is applied as one of the custom properties of the DWF6 ePlot pc3 file.
Before Beyond the Paper existed, I published a table of desirable DPI values on Shaan Hurley's Between the Lines Blog.
Check these old articles out. They still apply.