Same image want to display with different size in PDF. image size 20px in footer and 200px in page . In normal visualforce page it works fine but when rendered as PDF. it's not working, its overriding the footers height and width attribute values.
When you render VF page as PDF, layout gets changed by Salesforce internally- you need to update css accordingly. Here you go: https://help.salesforce.com/articleView?id=000004706&type=1