1. Copy the paper.
2. Line up the original and the copy (Arrange tab, Align vertically and horizontally).
3. Select the original and darken it just a little bit (Color tab, Brightness & Light) or click on Click & Fill, Color, Colors on this Page, select the darkest one, OK.
4. Select the copy and blur the outside edge (right click, edit image, using an image filter, edge, soften edge, pick a number and adjust if necessary).
5. Select both elements (on the element list on the left side of the screen the darker original should be below the softened copy), arrange, flatten and then add shadows if desired.
By the way, this works with any element that could use a bit of a darker, more defined border. If you want to use this method with text, you will have to flatten it first so it becomes an element. Filter options work on elements only.