Enable Measuring
Used to enable or disable measuring. If the Measuring property is set to On, the design file units are retained when you publish a DGN to a PDF document. If the Measuring property is set to Off, the PDF measuring tool will measure in inches.
In order to measure with Adobe Reader, the PDF needs to be Reader Enabled using Adobe Acrobat. This is accomplished by enabling the Enable Usage Rights in Adobe Reader option in Adobe Acrobat.