I need to update an existing URL I have inherited a Craft website and need to update an existing URL, it will open a PDF document, so I need to replace an updated PDF

I have very basic Craft knowledge so need assistance.  I have added a Screenshot below showing the inforamtion behind the link which I hope helps
You can replace a file directly in the control panel. Navigate to Assets, select the file you want to replace and then click the cog icon to select the “Replace file” action.