After watermark, page orientation changes

Sometimes, after watermarking a pdf whose orientation is landscape, the orientation changes to portrait.
As a result, some texts are hidden.
I have attached some images showing what I mean.
One of the image shows when the pdf (with landscape orientation) hasn't been watermarked.
While the other shows when the pdf has been watermarked and was changed to portrait, hence cutting off some texts.
Please look into this.
And most importantly, THANK YOU FOR THIS GREAT TOOL.