import PyPDF2

template = PyPDF2.PdfFileReader( open( 'combined.pdf', 'rb' ) )
watermark = PyPDF2.PdfFileReader( open( 'wtr.pdf', 'rb' ) )
output = PyPDF2.PdfFileWriter()

for i in range( template.getNumPages() ):
	page = template.getPage( i )
	page.mergePage( watermark.getPage(0) )
	output.addPage( page )

	with open( 'combined_watermarked.pdf', 'wb' ) as file:
		output.write( file )