Dimensions 
You can add dimensions as markup elements associated with comments.
To add dimensions to comments, Measure
must be enabled, as shown by Measure
Enabled 
in the status
bar.
Markup dimensions are for reference only. Editing the text does not modify
the model.
To add dimensions:
Activate a comment and click Dimension
(Markup tab 
) or Tools, Markup, Dimension.
In the dialog box, choose a selection filter (faces,
edges, vertices, or holes).
-
Select an item and click to place the extension lines and dimension
text.
A text box appears with the
dimension.
If Measure
is not enabled, as shown by the 
icon in the status bar,
a blank text box appears in the graphics area. You can type text in the
box.
Edit the dimension and add text, then click.
To edit a dimension:
To
edit dimension text, double-click it.
To
move dimension text, drag it.
To
move extension lines, drag the handles 
.
To
delete dimension text, select it and press Delete.