MAC's Page Curl I & Page Curl II  are freeware Page Curling filters made by Mark McLaren.

 Compatible with Paint Shop Pro. 
Just make sure you apply the filter Page Curl II (MPCurl.8bf) to the background layer, 

applying it to another layer will make the entire thing transparent. 

Maccurl and MPCurl will not work separately when in the same folder (PSP)
Mark also did MAC's Remove White 

Page Curl I 

Page Curl II

Control Size, Transparency, Shininess,

Shadow and Orientation

Control Size, Transparency, Shininess,

Shadow, Position, Vertical and Horizontal Orientation

Antialiasing Option

Remove White

Automatic Effect