One precaution in downloading patterns from the internet is that many printers print the patterns with slightly different measurements, because of printer settings differences.
One suggestion is to use old-fashioned grids in order to translate the pattern to the exact size that you need it to be. The website of http://www.dollstreetdreamers.com/gridclass1.htm, offers an on-line tutorial about using these grids. Another recommendation is to buy a
Proportional scale. These scales help you to reduce/enlarge patterns or can be used to determine the appropriate sizes of accessories for your stuffed animal.
When using either one of these two methods, you should not include the seam allowance because it will be distorted to a different size too. You should add the seam allowance as you are cutting out your fabric, by marking it directly on the fabric.