Hi everyone! I hope you will find this information useful. I had a very hard time figuring out how to remove the shadow texture from cold pressed watercolor paper. Here is what I now do.
My scanner is a Canon 9000F MarkII
Scan the image twice, once right side up and one upside down. Rotate the upside down one 180 degrees so it is right side up.
Add both images to Photoshop.
Select both layers
Rasterize all layers
Then auto align both layers
Set the top layers opacity to about 50% and merge down
Edit if needed