from aspose.cells import PaperSizeType, PdfSaveOptions, Workbook
from aspose.cells.rendering import RenderingWatermark

# prepare a workbook with 3 pages.
wb = Workbook()
wb.worksheets[0].cells.get("A1").put_value("Page1")
index = wb.worksheets.add()
wb.worksheets[index].cells.get("A1").put_value("Page2")
index = wb.worksheets.add()
wb.worksheets[index].cells.get("A1").put_value("Page3")
wb.worksheets[index].page_setup.paper_size = PaperSizeType.PAPER_A3
# create a watermark from image(you need to prepare image bytes).
watermark = RenderingWatermark(imageBytes)
# specify offset to alignment.
watermark.offset_x = 100.0
watermark.offset_y = 200.0
# specify rotation
watermark.rotation = 30.0
# specify watermark to background.
watermark.is_background = True
# specify opacity
watermark.opacity = 0.6
# specify the scale to page(e.g. 100, 50) in percent.
watermark.scale_to_page_percent = 50
# spcify watermark for rendering to pdf.
options = PdfSaveOptions()
options.watermark = watermark
wb.save("oputput_image_watermark.pdf", options)