You want to show both Imperial and Metric...
Assuming you haven't started your project yet, this will make adding alternate units as fast as possible in Revit. If you have already started your project, you will have to shift things around which really isn't much faster than the current wayanyway.
Set up your main dimension style up the way you like it. For example... But then double your Dimesnion line snap distance setting (might have to play with that distance to get most for your money in terms of space) Then when you dimension and you hit the snap distance it will look like this.... Looks a bit funny but bear with me.
Duplicate your main dimension syle...
Change the units to the opposite of your main style (in my case metric)
Set Tick Mark style to 'None'
Set the Dimension Line Extension to '0'
Set the Witness Line Control to 'Fixed to Dimension Line'
Set the Witness Line Length to '0'
Set the Witness Line Extension to '0'
Set the Text Offset to at least your Text Size + 2 times the text offset of you main dim style... adjust to suit your preferece.
Maybe set the font setting and or italics just to give a better visual difference.
Then when you dimension and hit your snaps with this style you might end up with something like this...
Now document your views with your main style. Once done. zoom out. do a crossing window and use the filter selection to just get the dimensions. Copy to clip board. Paste to current view. Don't click anywhere. Click on the type selector and set the type to your alternate dim type. and you end up with something like this...
Repeat from the selection process for the rest of your views.
If you want to put your alternate on the bottom instead of the top (right next to the dimension line) simply switch the text offsets to the other type in each dimension type.
I wish Revit would allow me to put a negative offset in for text offset and add prefix/suffix by type...then It could look just like a dual unit plan
Inspired by Steve's blog post here...Alternate units...Seriously?