For Windows
PDFelement 9
1. Click File and select Preference
2. Select Units & Grid and select the unit you would like to use.
3. Click Apply to confirm the change.
PDFelement 8
1. Click File on the upper left corner and select Preference.
2. Select General and change the Measurement Units that you need.
3. Click OK to confirm the change.
For Mac
Sorry to say that PDFelement Mac doesn't support the Measurement tool yet. We will try to add it in the future.