I have sewn doll clothes to sell for many years from commercial patterns .  If you have ever reused these tissue patterns over and over you KNOW that the wear on them is pretty severe.  To strengthen the patterns I iron the uncut tissue pattern sheets to a piece of iron on interfacing then cut out a nice sturdy, reinforced pattern piece that will stand up to MUCH handling and pinning.  The white background of the interfacing also makes the printed instructions on the pattern pieces much more readable.