Workable fixaive spray.
Use in a well ventilated area and away from other art. This spray will allow you to seal your pencil, pastel, and charcoal in place. The workable park means that you can continue to add to your piece if you'd like.
If you want to seal pieces in a book, use wax paper to cover the other leaves above and below so the rest remain workable. Leave the wax paper in place until the fixative dries. Bargain store wax paper works well for this purpose.
I do not use final fixative as it darkens work.
An alternative that people use is hairspray, this is a mistake. It never dries properly and usually remains tacky.