ParagraphFormat.LineSpacing Property (Word)
Returns or sets the line spacing (in points) for the specified paragraphs. Read/write Single.
Use the LinesToPoints method to convert a number of lines to the corresponding value in points. For example, LinesToPoints(2) returns the value 24.
The LineSpacing property can be set after the LineSpacingRule property has been set to:
wdLineSpaceAtLeast the line spacing can be greater than or equal to, but never less than, the specified LineSpacing value.
wdLineSpaceExactly the line spacing never changes from the specified LineSpacing value, even if a larger font is used within the paragraph.
wdLineSpaceMultiple a LineSpacing property value must be specified, in points.