Vellum paper has long been used as a fancy platform for invitations, letters and other formal correspondence. With the explosion of scrapbooking, folks have also turned to vellum paper for its lightweight, transparent nature and imprints of glorious designs. Other craft projects also do well with vellum paper, but any project can turn into an ugly mess if you incorrectly glue vellum paper. Since vellum will not absorb glue like other papers, vellum needs a special touch and a special adhesive.
Get your adhesive. Ordinary craft glues are going to glob and show through the vellum. Trek to your local arts and craft store to pick up specially formulated vellum adhesive. The adhesive, which is basically a transparent-drying double-sided tape, comes in rolls, sheets or even small dots to suit your crafting needs. It's also available online; see Resources below.
Prepare your paper. Cut and position the vellum paper on the page, ornament or project so you know where you want your glue to best secure it. Pick a few key points where adhesive will work best, such as at corners, in the middle and on jagged edges that look like they would eventually curl up.
Apply the adhesive. Cut or ready a small piece of the chosen adhesive, pulling off one side of the backing. Secure the sticky side to the corner or area where you want the vellum to stick on the backside of the vellum. Press firmly into place on its desired target.
Allow to dry fully. Leave your newly-glued vellum in the open air for a few minutes until the adhesive has fully adhered. Do not simply slam shut the scrapbook once you've applied the adhesive, or you may end up with bent vellum or pages sticking where you don't want them to stick.
Store unused adhesive sheets in an airtight bag so they can be used again.