From Scroll Saw Wiki
There are numerous way to apply you pattern for cutting. This is the best way I have found though. Cut your pattern out close around the edges of it. Apply masking, or painters tape to the wood over the area to be cut. Be sure to cover enough for the pattern to go on. There are varying opinions on brands and color of tape to use. I prefer the plain white tape simply because it's cheaper in my area. With the patter side down, spray the paper with spray adhesive. Once again, different opinions. I personally use nothing but 3M Super 77. Everytime I try straying to other brands, I have nothing but problems. Apply the pattern on the wood over the tape. Press down and smooth over with your hands. Have fun cutting. When finished, work up a corner with your finger nail and peal off. Sometimes the tape and pattern will tear off, especially around small cutouts. Just keep pulling up corners and removing until the entire pattern is removed.