You'll need adhesives to assemble certain printables, like attaching cupcake toppers to paper straws. A printable designer's go-to adhesive is usually a hot glue gun. They're inexpensive, and the glue is guaranteed to keep everything in place. You can also use glue dots, double sided tape (permanent is preferred), glue sticks, or regular tape.
However, if you want to create something custom to fit your needs, you can learn to create your own! You'll need to choose the right software and learning program, and you'll be well on your way to making amazing and unique printables.