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.