why take dead leaves? LOL.
take fresh leaves and slip them between 2 pieces of paper towel and place them between the pages of a phonebook.
then add more weights on top of that phonebook. (maybe stack more books on top or something)
will take around 2-3 weeks for the leaves to be completely pressed and dried.
so it will be better to get leaves with lower moisture content if you want the process to be faster.
after the leaves are pressed and dried, you can take them out and laminate the them to make into bookmarks.
the effect should be pretty good.