Why is line spacing different between printers in document... Office 2003

I have used Office 2000 and so on for years in the past. Now, when I am
setting up a document the line spacing seems to depend on the printer. With
one printer I need to use single line spacing and on another I'd need to use
..65 spacing to achive same results. THis has not happened before on my
previous PC using the same printers & drivers. This means I need to format
the document to the printer. I am aware there are slight changes when a
different printer is selected but this cause a 2 page document to go up to
2-3/4 pages... way out of wack.

Printers are Phasar 850
Epson 900
Canon Pixma 4000

Greg