How to Add a Stamp to a PDF

how can i make sure the chop size is the same every time i paste it

I tried to print a pdf receipt that had a stamp that said “paid”. When I printed the receipt, the stamp does not show up. How can I make the stamp show up on the printed copy?

What if the pdf contain multiple sheets ansd thé stamp must appair in all of them

What should be the size of signature and stamp?