It seems as though you're using ENTER to create a new line of text? If
this is what you're doing, it's the "typewriter approach" to word
processing. Instead, you should let Word flow the text from line to
line, which, among other things, allows you to add or delete text, use
justified text, change page margins and font sizes without constantly
adding and deleting paragraph breaks. Unlike a typewriter, Word needs
the ENTER key only to create a new paragraph.
If each paragraph of text is followed by a single paragraph break, you
can easily specify spacing between paragraphs as well as spacing
between lines. (If you use ENTER for "line creation" you never make
use of line spacing; instead, paragraph spacing is applied between
each line of text.) On the Format menu, click Paragraph. Specify the
desired paragraph spacing in the Space before and Space after boxes.
And specify the desired line spacing in the Line spacing box.